Ydb stable 23-1-2623.1.26

x-stable-origin-commit: 22184a7e157553d447f17a2dffc4ea2d32dfd74d

1 files changed, 5236 insertions, 0 deletions

diff --git a/contrib/libs/libfyaml/src/lib/fy-walk.c b/contrib/libs/libfyaml/src/lib/fy-walk.c
new file mode 100644
index 0000000000..d76125071e
--- /dev/null
+++ b/contrib/libs/libfyaml/src/lib/fy-walk.c
@@ -0,0 +1,5236 @@
+/*
+ * fy-walk.c - path walker
+ *
+ * Copyright (c) 2021 Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <errno.h>
+#if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
+#include <unistd.h>
+#endif
+#include <math.h>
+#include <limits.h>
+
+#include <libfyaml.h>
+
+#include "fy-parse.h"
+#include "fy-doc.h"
+#include "fy-walk.h"
+
+#include "fy-utils.h"
+
+#undef DEBUG_EXPR
+// #define DEBUG_EXPR
+
+const char *fy_walk_result_type_txt[FWRT_COUNT] = {
+	[fwrt_none]	= "none",
+	[fwrt_node_ref]	= "node-ref",
+	[fwrt_number]	= "number",
+	[fwrt_string]	= "string",
+	[fwrt_doc]	= "doc",
+	[fwrt_refs]	= "refs",
+};
+
+void fy_walk_result_dump(struct fy_walk_result *fwr, struct fy_diag *diag, enum fy_error_type errlevel, int level,
+		const char *fmt, ...);
+
+void fy_walk_result_vdump(struct fy_walk_result *fwr, struct fy_diag *diag, enum fy_error_type errlevel, int level,
+		const char *fmt, va_list ap)
+{
+	struct fy_walk_result *fwr2;
+	char *banner;
+	char *texta = NULL;
+	const char *text = "";
+	size_t len;
+	bool save_on_error;
+	char buf[30];
+	int rc __FY_DEBUG_UNUSED__;
+
+	if (!diag)
+		return;
+
+	if (errlevel < diag->cfg.level)
+		return;
+
+	save_on_error = diag->on_error;
+	diag->on_error = true;
+
+	if (fmt) {
+		banner = NULL;
+		rc = vasprintf(&banner, fmt, ap);
+		assert(rc != -1);
+		assert(banner);
+		fy_diag_diag(diag, errlevel, "%-*s%s", level*2, "", banner);
+		free(banner);
+	}
+	if (!fwr)
+		goto out;
+
+	switch (fwr->type) {
+	case fwrt_none:
+		text="";
+		break;
+	case fwrt_node_ref:
+		texta = fy_node_get_path(fwr->fyn);
+		assert(texta);
+		text = texta;
+		break;
+	case fwrt_number:
+		snprintf(buf, sizeof(buf), "%f", fwr->number);
+		text = buf;
+		break;
+	case fwrt_string:
+		text = fwr->string;
+		break;
+	case fwrt_doc:
+		texta = fy_emit_document_to_string(fwr->fyd, FYECF_WIDTH_INF | FYECF_INDENT_DEFAULT | FYECF_MODE_FLOW_ONELINE);
+		assert(texta);
+		text = texta;
+		break;
+	case fwrt_refs:
+		text="";
+		break;
+	}
+
+	len = strlen(text);
+
+	fy_diag_diag(diag, errlevel, "%-*s%s%s%.*s",
+			(level + 1) * 2, "",
+			fy_walk_result_type_txt[fwr->type],
+			len ? " " : "",
+			(int)len, text);
+
+	if (texta)
+		free(texta);
+
+	if (fwr->type == fwrt_refs) {
+		for (fwr2 = fy_walk_result_list_head(&fwr->refs); fwr2; fwr2 = fy_walk_result_next(&fwr->refs, fwr2))
+			fy_walk_result_dump(fwr2, diag, errlevel, level + 1, NULL);
+	}
+out:
+	diag->on_error = save_on_error;
+}
+
+void fy_walk_result_dump(struct fy_walk_result *fwr, struct fy_diag *diag, enum fy_error_type errlevel, int level,
+		const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	fy_walk_result_vdump(fwr, diag, errlevel, level, fmt, ap);
+	va_end(ap);
+}
+
+/* NOTE that walk results do not take references and it is invalid to
+ * use _any_ call that modifies the document structure
+ */
+struct fy_walk_result *fy_walk_result_alloc_rl(struct fy_walk_result_list *fwrl)
+{
+	struct fy_walk_result *fwr = NULL;
+
+	if (fwrl)
+		fwr = fy_walk_result_list_pop(fwrl);
+
+	if (!fwr) {
+		fwr = malloc(sizeof(*fwr));
+		if (!fwr)
+			return NULL;
+		memset(fwr, 0, sizeof(*fwr));
+	}
+	fwr->type = fwrt_none;
+	return fwr;
+}
+
+struct fy_walk_result *fy_walk_result_clone_rl(struct fy_walk_result_list *fwrl, struct fy_walk_result *fwr)
+{
+	struct fy_walk_result *fwrn = NULL, *fwrn2 = NULL, *fwrn3;
+
+	if (!fwr)
+		return NULL;
+
+	fwrn = fy_walk_result_alloc_rl(fwrl);
+	if (!fwrn)
+		return NULL;
+
+	fwrn->type = fwr->type;
+	switch (fwr->type) {
+	case fwrt_none:
+		break;
+	case fwrt_node_ref:
+		fwrn->fyn = fwr->fyn;
+		break;
+	case fwrt_number:
+		fwrn->number = fwr->number;
+		break;
+	case fwrt_string:
+		fwrn->string = strdup(fwr->string);
+		if (!fwrn->string)
+			goto err_out;
+		break;
+	case fwrt_doc:
+		fwrn->fyd = fy_document_clone(fwr->fyd);
+		if (!fwrn->fyd)
+			goto err_out;
+		break;
+	case fwrt_refs:
+
+		fy_walk_result_list_init(&fwrn->refs);
+
+		for (fwrn2 = fy_walk_result_list_head(&fwr->refs); fwrn2;
+			fwrn2 = fy_walk_result_next(&fwr->refs, fwrn2)) {
+
+			fwrn3 = fy_walk_result_clone_rl(fwrl, fwrn2);
+			if (!fwrn3)
+				goto err_out;
+
+			fy_walk_result_list_add_tail(&fwrn->refs, fwrn3);
+		}
+		break;
+	}
+	return fwrn;
+err_out:
+	if (fwrn)
+		fy_walk_result_free_rl(fwrl, fwrn);
+	return NULL;
+}
+
+struct fy_walk_result *fy_walk_result_clone(struct fy_walk_result *fwr)
+{
+	struct fy_walk_result_list *fwrl;
+
+	if (!fwr)
+		return NULL;
+
+	fwrl = fy_path_exec_walk_result_rl(fwr->fypx);
+	return fy_walk_result_clone_rl(fwrl, fwr);
+}
+
+void fy_walk_result_clean_rl(struct fy_walk_result_list *fwrl, struct fy_walk_result *fwr)
+{
+	struct fy_walk_result *fwrn;
+
+	if (!fwr)
+		return;
+
+	switch (fwr->type) {
+	case fwrt_none:
+		break;
+	case fwrt_node_ref:
+	case fwrt_number:
+		break;
+	case fwrt_string:
+		if (fwr->string)
+			free(fwr->string);
+		break;
+	case fwrt_doc:
+		if (fwr->fyd)
+			fy_document_destroy(fwr->fyd);
+		break;
+	case fwrt_refs:
+		while ((fwrn = fy_walk_result_list_pop(&fwr->refs)) != NULL)
+			fy_walk_result_free_rl(fwrl, fwrn);
+		break;
+	}
+
+	fwr->type = fwrt_none;
+}
+
+void fy_walk_result_clean(struct fy_walk_result *fwr)
+{
+	struct fy_walk_result_list *fwrl;
+
+	if (!fwr)
+		return;
+
+	fwrl = fy_path_exec_walk_result_rl(fwr->fypx);
+	fy_walk_result_clean_rl(fwrl, fwr);
+}
+
+void fy_walk_result_free_rl(struct fy_walk_result_list *fwrl, struct fy_walk_result *fwr)
+{
+	struct fy_path_exec *fypx;
+
+	if (!fwr)
+		return;
+
+	fypx = fwr->fypx;
+
+	fy_walk_result_clean_rl(fwrl, fwr);
+
+	if (fwrl)
+		fy_walk_result_list_push(fwrl, fwr);
+	else
+		free(fwr);
+
+	fy_path_exec_unref(fypx);	/* NULL is OK */
+}
+
+void fy_walk_result_free(struct fy_walk_result *fwr)
+{
+	struct fy_walk_result_list *fwrl;
+
+	if (!fwr)
+		return;
+
+	fwrl = fy_path_exec_walk_result_rl(fwr->fypx);
+	fy_walk_result_free_rl(fwrl, fwr);
+}
+
+void fy_walk_result_list_free_rl(struct fy_walk_result_list *fwrl, struct fy_walk_result_list *results)
+{
+	struct fy_walk_result *fwr;
+
+	while ((fwr = fy_walk_result_list_pop(results)) != NULL)
+		fy_walk_result_free_rl(fwrl, fwr);
+}
+
+struct fy_walk_result *fy_walk_result_vcreate_rl(struct fy_walk_result_list *fwrl, enum fy_walk_result_type type, va_list ap)
+{
+	struct fy_walk_result *fwr = NULL;
+
+	if ((unsigned int)type >= FWRT_COUNT)
+		goto err_out;
+
+	fwr = fy_walk_result_alloc_rl(fwrl);
+	if (!fwr)
+		goto err_out;
+
+	fwr->type = type;
+
+	switch (fwr->type) {
+	case fwrt_none:
+		break;
+	case fwrt_node_ref:
+		fwr->fyn = va_arg(ap, struct fy_node *);
+		break;
+	case fwrt_number:
+		fwr->number = va_arg(ap, double);
+		break;
+	case fwrt_string:
+		fwr->string = strdup(va_arg(ap, const char *));
+		if (!fwr->string)
+			goto err_out;
+		break;
+	case fwrt_doc:
+		fwr->fyd = va_arg(ap, struct fy_document *);
+		break;
+	case fwrt_refs:
+		fy_walk_result_list_init(&fwr->refs);
+		break;
+	}
+
+	return fwr;
+
+err_out:
+	fy_walk_result_free_rl(fwrl, fwr);
+
+	return NULL;
+}
+
+struct fy_walk_result *fy_walk_result_create_rl(struct fy_walk_result_list *fwrl, enum fy_walk_result_type type, ...)
+{
+	struct fy_walk_result *fwr;
+	va_list ap;
+
+	va_start(ap, type);
+	fwr = fy_walk_result_vcreate_rl(fwrl, type, ap);
+	va_end(ap);
+
+	return fwr;
+}
+
+void fy_walk_result_flatten_internal(struct fy_walk_result *fwr, struct fy_walk_result *fwrf)
+{
+	struct fy_walk_result *fwr2, *fwr2n;
+
+	if (!fwr || !fwrf || fwr->type != fwrt_refs)
+		return;
+
+	for (fwr2 = fy_walk_result_list_head(&fwr->refs); fwr2; fwr2 = fwr2n) {
+
+		fwr2n = fy_walk_result_next(&fwr->refs, fwr2);
+
+		if (fwr2->type != fwrt_refs) {
+			fy_walk_result_list_del(&fwr->refs, fwr2);
+			fy_walk_result_list_add_tail(&fwrf->refs, fwr2);
+			continue;
+		}
+		fy_walk_result_flatten_internal(fwr2, fwrf);
+	}
+}
+
+bool fy_walk_result_has_leaves_only(struct fy_walk_result *fwr)
+{
+	struct fy_walk_result *fwrn;
+
+	if (!fwr || fwr->type != fwrt_refs)
+		return false;
+
+	if (fy_walk_result_list_empty(&fwr->refs))
+		return false;
+
+	for (fwrn = fy_walk_result_list_head(&fwr->refs); fwrn;
+			fwrn = fy_walk_result_next(&fwr->refs, fwrn)) {
+
+		if (fwrn->type == fwrt_refs)
+			return false;
+	}
+
+	return true;
+}
+
+struct fy_walk_result *
+fy_walk_result_flatten_rl(struct fy_walk_result_list *fwrl, struct fy_walk_result *fwr)
+{
+	struct fy_walk_result *fwrf;
+
+	if (!fwr)
+		return NULL;
+
+	fwrf = fy_walk_result_create_rl(fwrl, fwrt_refs);
+	assert(fwrf);
+
+	fy_walk_result_flatten_internal(fwr, fwrf);
+	fy_walk_result_free_rl(fwrl, fwr);
+	return fwrf;
+}
+
+struct fy_walk_result *
+fy_walk_result_flatten(struct fy_walk_result *fwr)
+{
+	struct fy_walk_result_list *fwrl;
+
+	if (!fwr)
+		return NULL;
+
+	fwrl = fy_path_exec_walk_result_rl(fwr->fypx);
+	return fy_walk_result_flatten_rl(fwrl, fwr);
+}
+
+struct fy_node *
+fy_walk_result_node_iterate(struct fy_walk_result *fwr, void **prevp)
+{
+	struct fy_walk_result *fwrn;
+
+	if (!fwr || !prevp)
+		return NULL;
+
+	switch (fwr->type) {
+	case fwrt_node_ref:
+		if (!*prevp) {
+			*prevp = fwr;
+			return fwr->fyn;
+		}
+		*prevp = NULL;
+		return NULL;
+
+	case fwrt_refs:
+		if (!*prevp)
+			fwrn = fy_walk_result_list_head(&fwr->refs);
+		else
+			fwrn = fy_walk_result_next(&fwr->refs, *prevp);
+
+		/* skip over any non node refs */
+		while (fwrn && fwrn->type != fwrt_node_ref)
+			fwrn = fy_walk_result_next(&fwr->refs, fwrn);
+		*prevp = fwrn;
+		return fwrn ? fwrn->fyn : NULL;
+
+	default:
+		break;
+	}
+
+	return NULL;
+}
+
+const char *fy_path_expr_type_txt[FPET_COUNT] = {
+	[fpet_none]			= "none",
+	/* */
+	[fpet_root]			= "root",
+	[fpet_this]			= "this",
+	[fpet_parent]			= "parent",
+	[fpet_every_child]		= "every-child",
+	[fpet_every_child_r]		= "every-child-recursive",
+	[fpet_filter_collection]	= "filter-collection",
+	[fpet_filter_scalar]		= "filter-scalar",
+	[fpet_filter_sequence]		= "filter-sequence",
+	[fpet_filter_mapping]		= "filter-mapping",
+	[fpet_filter_unique]		= "filter-unique",
+	[fpet_seq_index]		= "seq-index",
+	[fpet_seq_slice]		= "seq-slice",
+	[fpet_alias]			= "alias",
+
+	[fpet_map_key]			= "map-key",
+
+	[fpet_multi]			= "multi",
+	[fpet_chain]			= "chain",
+	[fpet_logical_or]		= "logical-or",
+	[fpet_logical_and]		= "logical-and",
+
+	[fpet_eq]			= "equals",
+	[fpet_neq]			= "not-equals",
+	[fpet_lt]			= "less-than",
+	[fpet_gt]			= "greater-than",
+	[fpet_lte]			= "less-or-equal-than",
+	[fpet_gte]			= "greater-or-equal-than",
+
+	[fpet_scalar]			= "scalar",
+
+	[fpet_plus]			= "plus",
+	[fpet_minus]			= "minus",
+	[fpet_mult]			= "multiply",
+	[fpet_div]			= "divide",
+
+	[fpet_lparen]			= "left-parentheses",
+	[fpet_rparen]			= "right-parentheses",
+	[fpet_method]			= "method",
+
+	[fpet_scalar_expr]		= "scalar-expression",
+	[fpet_path_expr]		= "path-expression",
+	[fpet_arg_separator]		= "argument-separator",
+};
+
+struct fy_path_expr *fy_path_expr_alloc(void)
+{
+	struct fy_path_expr *expr = NULL;
+
+	expr = malloc(sizeof(*expr));
+	if (!expr)
+		return NULL;
+	memset(expr, 0, sizeof(*expr));
+	fy_path_expr_list_init(&expr->children);
+
+	return expr;
+}
+
+void fy_path_expr_free(struct fy_path_expr *expr)
+{
+	struct fy_path_expr *exprn;
+
+	if (!expr)
+		return;
+
+	while ((exprn = fy_path_expr_list_pop(&expr->children)) != NULL)
+		fy_path_expr_free(exprn);
+
+	fy_token_unref(expr->fyt);
+
+	free(expr);
+}
+
+struct fy_path_expr *fy_path_expr_alloc_recycle(struct fy_path_parser *fypp)
+{
+	struct fy_path_expr *expr = NULL;
+
+	if (!fypp || fypp->suppress_recycling)
+		expr = fy_path_expr_alloc();
+
+	if (!expr) {
+		expr = fy_path_expr_list_pop(&fypp->expr_recycle);
+		if (expr) {
+			memset(expr, 0, sizeof(*expr));
+			fy_path_expr_list_init(&expr->children);
+		} else
+			expr = fy_path_expr_alloc();
+	}
+
+	if (!expr)
+		return NULL;
+
+	expr->expr_mode = fypp->expr_mode;
+
+	return expr;
+}
+
+void fy_path_expr_free_recycle(struct fy_path_parser *fypp, struct fy_path_expr *expr)
+{
+	struct fy_path_expr *exprn;
+
+	if (!fypp || fypp->suppress_recycling) {
+		fy_path_expr_free(expr);
+		return;
+	}
+
+	while ((exprn = fy_path_expr_list_pop(&expr->children)) != NULL)
+		fy_path_expr_free_recycle(fypp, exprn);
+
+	if (expr->fyt) {
+		fy_token_unref(expr->fyt);
+		expr->fyt = NULL;
+	}
+	fy_path_expr_list_add_tail(&fypp->expr_recycle, expr);
+}
+
+void fy_expr_stack_setup(struct fy_expr_stack *stack)
+{
+	if (!stack)
+		return;
+
+	memset(stack, 0, sizeof(*stack));
+	stack->items = stack->items_static;
+	stack->alloc = ARRAY_SIZE(stack->items_static);
+}
+
+void fy_expr_stack_cleanup(struct fy_expr_stack *stack)
+{
+	if (!stack)
+		return;
+
+	while (stack->top > 0)
+		fy_path_expr_free(stack->items[--stack->top]);
+
+	if (stack->items != stack->items_static)
+		free(stack->items);
+	stack->items = stack->items_static;
+	stack->alloc = ARRAY_SIZE(stack->items_static);
+}
+
+void fy_expr_stack_dump(struct fy_diag *diag, struct fy_expr_stack *stack)
+{
+	struct fy_path_expr *expr;
+	unsigned int i;
+
+	if (!stack)
+		return;
+
+	if (!stack->top)
+		return;
+
+	i = stack->top;
+	do {
+		expr = stack->items[--i];
+		fy_path_expr_dump(expr, diag, FYET_NOTICE, 0, NULL);
+	} while (i > 0);
+}
+
+int fy_expr_stack_size(struct fy_expr_stack *stack)
+{
+	if (!stack || stack->top >= (unsigned int)INT_MAX)
+		return -1;
+	return (int)stack->top;
+}
+
+int fy_expr_stack_push(struct fy_expr_stack *stack, struct fy_path_expr *expr)
+{
+	struct fy_path_expr **items_new;
+	unsigned int alloc;
+	size_t size;
+
+	if (!stack || !expr)
+		return -1;
+
+	assert(stack->items);
+	assert(stack->alloc > 0);
+
+	assert(expr->fyt);
+
+	/* grow the stack if required */
+	if (stack->top >= stack->alloc) {
+		alloc = stack->alloc;
+		size = alloc * sizeof(*items_new);
+
+		if (stack->items == stack->items_static) {
+			items_new = malloc(size * 2);
+			if (items_new)
+				memcpy(items_new, stack->items_static, size);
+		} else
+			items_new = realloc(stack->items, size * 2);
+
+		if (!items_new)
+			return -1;
+
+		stack->alloc = alloc * 2;
+		stack->items = items_new;
+	}
+
+	stack->items[stack->top++] = expr;
+
+	return 0;
+}
+
+struct fy_path_expr *fy_expr_stack_peek_at(struct fy_expr_stack *stack, unsigned int pos)
+{
+	if (!stack || stack->top <= pos)
+		return NULL;
+	return stack->items[stack->top - 1 - pos];
+}
+
+struct fy_path_expr *fy_expr_stack_peek(struct fy_expr_stack *stack)
+{
+	return fy_expr_stack_peek_at(stack, 0);
+}
+
+struct fy_path_expr *fy_expr_stack_pop(struct fy_expr_stack *stack)
+{
+	if (!stack || !stack->top)
+		return NULL;
+
+	return stack->items[--stack->top];
+}
+
+bool fy_token_type_can_be_path_expr(enum fy_token_type type)
+{
+	return type == FYTT_NONE ||
+	       type == FYTT_PE_LPAREN ||
+	       type == FYTT_PE_RPAREN ||
+	       type == FYTT_PE_EQEQ ||
+	       type == FYTT_PE_NOTEQ ||
+	       type == FYTT_PE_GT ||
+	       type == FYTT_PE_LT ||
+	       type == FYTT_PE_GTE ||
+	       type == FYTT_PE_LTE ||
+	       type == FYTT_PE_METHOD;
+}
+
+bool fy_token_type_can_be_before_negative_number(enum fy_token_type type)
+{
+	return type == FYTT_NONE ||
+	       type == FYTT_PE_LPAREN ||
+	       type == FYTT_PE_RPAREN ||
+	       type == FYTT_PE_EQEQ ||
+	       type == FYTT_PE_NOTEQ ||
+	       type == FYTT_PE_GT ||
+	       type == FYTT_PE_LT ||
+	       type == FYTT_PE_GTE ||
+	       type == FYTT_PE_LTE ||
+	       type == FYTT_SE_PLUS ||
+	       type == FYTT_SE_MINUS ||
+	       type == FYTT_SE_MULT ||
+	       type == FYTT_SE_DIV ||
+
+	       type == FYTT_SE_METHOD;
+}
+
+const char *fy_expr_mode_txt[FYEM_COUNT] = {
+	[fyem_none]	= "none",
+	[fyem_path]	= "path",
+	[fyem_scalar]	= "scalar",
+};
+
+static struct fy_diag *fy_path_parser_reader_get_diag(struct fy_reader *fyr)
+{
+	struct fy_path_parser *fypp = fy_container_of(fyr, struct fy_path_parser, reader);
+	return fypp->cfg.diag;
+}
+
+static const struct fy_reader_ops fy_path_parser_reader_ops = {
+	.get_diag = fy_path_parser_reader_get_diag,
+};
+
+void fy_path_parser_setup(struct fy_path_parser *fypp, const struct fy_path_parse_cfg *pcfg)
+{
+	if (!fypp)
+		return;
+
+	memset(fypp, 0, sizeof(*fypp));
+	if (pcfg)
+		fypp->cfg = *pcfg;
+	fy_reader_setup(&fypp->reader, &fy_path_parser_reader_ops);
+	fy_token_list_init(&fypp->queued_tokens);
+	fypp->last_queued_token_type = FYTT_NONE;
+
+	fy_expr_stack_setup(&fypp->operators);
+	fy_expr_stack_setup(&fypp->operands);
+
+	fy_path_expr_list_init(&fypp->expr_recycle);
+	fypp->suppress_recycling = (fypp->cfg.flags & FYPPCF_DISABLE_RECYCLING) || getenv("FY_VALGRIND");
+
+	fypp->expr_mode = fyem_path;
+	fypp->paren_nest_level = 0;
+}
+
+void fy_path_parser_cleanup(struct fy_path_parser *fypp)
+{
+	struct fy_path_expr *expr;
+
+	if (!fypp)
+		return;
+
+	fy_expr_stack_cleanup(&fypp->operands);
+	fy_expr_stack_cleanup(&fypp->operators);
+
+	fy_reader_cleanup(&fypp->reader);
+	fy_token_list_unref_all(&fypp->queued_tokens);
+
+	while ((expr = fy_path_expr_list_pop(&fypp->expr_recycle)) != NULL)
+		fy_path_expr_free(expr);
+
+	fypp->last_queued_token_type = FYTT_NONE;
+	fypp->stream_start_produced = false;
+	fypp->stream_end_produced = false;
+	fypp->stream_error = false;
+	fypp->token_activity_counter = 0;
+	fypp->paren_nest_level = 0;
+}
+
+int fy_path_parser_open(struct fy_path_parser *fypp,
+			struct fy_input *fyi, const struct fy_reader_input_cfg *icfg)
+{
+	int ret;
+	if (!fypp)
+		return -1;
+
+	ret = fy_reader_input_open(&fypp->reader, fyi, icfg);
+	if (ret)
+		return ret;
+	/* take a reference to the input */
+	fypp->fyi = fy_input_ref(fyi);
+	return 0;
+}
+
+void fy_path_parser_close(struct fy_path_parser *fypp)
+{
+	if (!fypp)
+		return;
+
+	fy_input_unref(fypp->fyi);
+
+	fy_reader_input_done(&fypp->reader);
+}
+
+struct fy_token *fy_path_token_vqueue(struct fy_path_parser *fypp, enum fy_token_type type, va_list ap)
+{
+	struct fy_token *fyt;
+
+	fyt = fy_token_list_vqueue(&fypp->queued_tokens, type, ap);
+	if (fyt) {
+		fypp->token_activity_counter++;
+		fypp->last_queued_token_type = type;
+	}
+	return fyt;
+}
+
+struct fy_token *fy_path_token_queue(struct fy_path_parser *fypp, enum fy_token_type type, ...)
+{
+	va_list ap;
+	struct fy_token *fyt;
+
+	va_start(ap, type);
+	fyt = fy_path_token_vqueue(fypp, type, ap);
+	va_end(ap);
+
+	return fyt;
+}
+
+int fy_path_fetch_seq_index_or_slice(struct fy_path_parser *fypp, int c)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt;
+	bool neg;
+	int i, j, val, nval, digits, indices[2];
+
+	fyr = &fypp->reader;
+
+	/* verify that the called context is correct */
+	assert(fy_is_num(c) || (c == '-' && fy_is_num(fy_reader_peek_at(fyr, 1))));
+
+	i = 0;
+	indices[0] = indices[1] = -1;
+
+	j = 0;
+	while (j < 2) {
+
+		neg = false;
+		if (c == '-') {
+			neg = true;
+			i++;
+		}
+
+		digits = 0;
+		val = 0;
+		while (fy_is_num((c = fy_reader_peek_at(fyr, i)))) {
+			nval = (val * 10) | (c - '0');
+			FYR_PARSE_ERROR_CHECK(fyr, 0, i, FYEM_SCAN,
+					nval >= val && nval >= 0, err_out,
+					"illegal sequence index (overflow)");
+			val = nval;
+			i++;
+			digits++;
+		}
+		FYR_PARSE_ERROR_CHECK(fyr, 0, i, FYEM_SCAN,
+				(val == 0 && digits == 1) || (val > 0), err_out,
+				"bad number");
+		if (neg)
+			val = -val;
+
+		indices[j] = val;
+
+		/* continue only on slice : */
+		if (c == ':') {
+			c = fy_reader_peek_at(fyr, i + 1);
+			if (fy_is_num(c) || (c == '-' && fy_is_num(fy_reader_peek_at(fyr, i + 2)))) {
+				i++;
+				j++;
+				continue;
+			}
+		}
+
+		break;
+	}
+
+	if (j >= 1)
+		fyt = fy_path_token_queue(fypp, FYTT_PE_SEQ_SLICE, fy_reader_fill_atom_a(fyr, i), indices[0], indices[1]);
+	else
+		fyt = fy_path_token_queue(fypp, FYTT_PE_SEQ_INDEX, fy_reader_fill_atom_a(fyr, i), indices[0]);
+
+	fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+	return 0;
+
+err_out:
+	fypp->stream_error = true;
+	return -1;
+}
+
+int fy_path_fetch_plain_or_method(struct fy_path_parser *fypp, int c,
+				  enum fy_token_type fytt_plain,
+				  enum fy_token_type fytt_method)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt;
+	struct fy_atom *handlep;
+	int i;
+	enum fy_token_type type;
+
+	fyr = &fypp->reader;
+
+	assert(fy_is_first_alpha(c));
+
+	type = fytt_plain;
+
+	i = 1;
+	while (fy_is_alnum(fy_reader_peek_at(fyr, i)))
+		i++;
+
+	if (fy_reader_peek_at(fyr, i) == '(')
+		type = fytt_method;
+
+	handlep = fy_reader_fill_atom_a(fyr, i);
+	if (type == FYTT_SCALAR) {
+		fyt = fy_path_token_queue(fypp, FYTT_SCALAR, handlep, FYSS_PLAIN, NULL);
+		fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+	} else {
+		fyt = fy_path_token_queue(fypp, type, handlep, NULL);
+		fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+	}
+
+	return 0;
+
+err_out:
+	fypp->stream_error = true;
+	return -1;
+}
+
+int fy_path_fetch_dot_method(struct fy_path_parser *fypp, int c, enum fy_token_type fytt)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt;
+	struct fy_atom *handlep;
+	int i;
+
+	fyr = &fypp->reader;
+
+	assert(c == '.');
+	fy_reader_advance(fyr, c);
+	c = fy_reader_peek(fyr);
+	assert(fy_is_first_alpha(c));
+
+	/* verify that the called context is correct */
+	i = 1;
+	while (fy_is_alnum(fy_reader_peek_at(fyr, i)))
+		i++;
+
+	handlep = fy_reader_fill_atom_a(fyr, i);
+
+	fyt = fy_path_token_queue(fypp, fytt, handlep, NULL);
+	fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+	return 0;
+
+err_out:
+	fypp->stream_error = true;
+	return -1;
+}
+
+int fy_path_fetch_flow_document(struct fy_path_parser *fypp, int c, enum fy_token_type fytt)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt;
+	struct fy_document *fyd;
+	struct fy_atom handle;
+	struct fy_parser fyp_data, *fyp = &fyp_data;
+	struct fy_parse_cfg cfg_data, *cfg = NULL;
+	int rc;
+
+	fyr = &fypp->reader;
+
+	/* verify that the called context is correct */
+	assert(fy_is_path_flow_key_start(c));
+
+	fy_reader_fill_atom_start(fyr, &handle);
+
+	cfg = &cfg_data;
+	memset(cfg, 0, sizeof(*cfg));
+	cfg->flags = FYPCF_DEFAULT_PARSE;
+	cfg->diag = fypp->cfg.diag;
+
+	rc = fy_parse_setup(fyp, cfg);
+	fyr_error_check(fyr, !rc, err_out, "fy_parse_setup() failed\n");
+
+	/* associate with reader and set flow mode */
+	fy_parser_set_reader(fyp, fyr);
+	fy_parser_set_flow_only_mode(fyp, true);
+
+	fyd = fy_parse_load_document(fyp);
+
+	/* cleanup the parser no matter what */
+	fy_parse_cleanup(fyp);
+
+	fyr_error_check(fyr, fyd, err_out, "fy_parse_load_document() failed\n");
+
+	fy_reader_fill_atom_end(fyr, &handle);
+
+	/* document is NULL, is a simple key */
+	fyt = fy_path_token_queue(fypp, fytt, &handle, fyd);
+	fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+	return 0;
+
+err_out:
+	fypp->stream_error = true;
+	return -1;
+}
+
+int fy_path_fetch_flow_map_key(struct fy_path_parser *fypp, int c)
+{
+	return fy_path_fetch_flow_document(fypp, c, FYTT_PE_MAP_KEY);
+}
+
+int fy_path_fetch_flow_scalar(struct fy_path_parser *fypp, int c)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt;
+	struct fy_atom handle;
+	bool is_single;
+	int rc = -1;
+
+	fyr = &fypp->reader;
+
+	/* verify that the called context is correct */
+	assert(fy_is_path_flow_scalar_start(c));
+
+	is_single = c == '\'';
+
+	rc = fy_reader_fetch_flow_scalar_handle(fyr, c, 0, &handle, false);
+	if (rc)
+		goto err_out_rc;
+
+	/* document is NULL, is a simple key */
+	fyt = fy_path_token_queue(fypp, FYTT_SCALAR, &handle, is_single ? FYSS_SINGLE_QUOTED : FYSS_DOUBLE_QUOTED);
+	fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+	return 0;
+
+err_out:
+	rc = -1;
+err_out_rc:
+	fypp->stream_error = true;
+	return rc;
+}
+
+int fy_path_fetch_number(struct fy_path_parser *fypp, int c)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt;
+	int i, digits;
+
+	fyr = &fypp->reader;
+
+	/* verify that the called context is correct */
+	assert(fy_is_num(c) || (c == '-' && fy_is_num(fy_reader_peek_at(fyr, 1))));
+
+	i = 0;
+	if (c == '-')
+		i++;
+
+	digits = 0;
+	while (fy_is_num((c = fy_reader_peek_at(fyr, i)))) {
+		i++;
+		digits++;
+	}
+	FYR_PARSE_ERROR_CHECK(fyr, 0, i, FYEM_SCAN,
+			digits > 0, err_out,
+			"bad number");
+
+	fyt = fy_path_token_queue(fypp, FYTT_SCALAR, fy_reader_fill_atom_a(fyr, i), FYSS_PLAIN);
+	fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+	return 0;
+
+err_out:
+	fypp->stream_error = true;
+	return -1;
+}
+
+int fy_path_fetch_tokens(struct fy_path_parser *fypp)
+{
+	enum fy_token_type type;
+	struct fy_token *fyt;
+	struct fy_reader *fyr;
+	int c, cn, rc, simple_token_count;
+
+	fyr = &fypp->reader;
+	if (!fypp->stream_start_produced) {
+
+		fyt = fy_path_token_queue(fypp, FYTT_STREAM_START, fy_reader_fill_atom_a(fyr, 0));
+		fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+		fypp->stream_start_produced = true;
+		return 0;
+	}
+
+	/* XXX scan to next token? */
+
+	c = fy_reader_peek(fyr);
+
+	if (fy_is_z(c)) {
+
+		if (c >= 0)
+			fy_reader_advance(fyr, c);
+
+		/* produce stream end continuously */
+		fyt = fy_path_token_queue(fypp, FYTT_STREAM_END, fy_reader_fill_atom_a(fyr, 0));
+		fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+		return 0;
+	}
+
+	fyt = NULL;
+	type = FYTT_NONE;
+	simple_token_count = 0;
+
+	/* first do the common tokens */
+	switch (c) {
+	case ',':
+		type = FYTT_PE_COMMA;
+		simple_token_count = 1;
+		break;
+
+	case '|':
+		if (fy_reader_peek_at(fyr, 1) == '|') {
+			type = FYTT_PE_BARBAR;
+			simple_token_count = 2;
+			break;
+		}
+		break;
+
+	case '&':
+		if (fy_reader_peek_at(fyr, 1) == '&') {
+			type = FYTT_PE_AMPAMP;
+			simple_token_count = 2;
+			break;
+		}
+		break;
+
+	case '(':
+		type = FYTT_PE_LPAREN;
+		simple_token_count = 1;
+		break;
+
+	case ')':
+		type = FYTT_PE_RPAREN;
+		simple_token_count = 1;
+		break;
+
+	case '=':
+		cn = fy_reader_peek_at(fyr, 1);
+		if (cn == '=') {
+			type = FYTT_PE_EQEQ;
+			simple_token_count = 2;
+			break;
+		}
+		break;
+
+	case '>':
+		cn = fy_reader_peek_at(fyr, 1);
+		if (cn == '=') {
+			type = FYTT_PE_GTE;
+			simple_token_count = 2;
+			break;
+		}
+		type = FYTT_PE_GT;
+		simple_token_count = 1;
+		break;
+
+	case '<':
+		cn = fy_reader_peek_at(fyr, 1);
+		if (cn == '=') {
+			type = FYTT_PE_LTE;
+			simple_token_count = 2;
+			break;
+		}
+		type = FYTT_PE_LT;
+		simple_token_count = 1;
+		break;
+
+	case '!':
+		cn = fy_reader_peek_at(fyr, 1);
+		if (cn == '=') {
+			type = FYTT_PE_NOTEQ;
+			simple_token_count = 2;
+			break;
+		}
+		/* may still be something else */
+		break;
+
+	default:
+		break;
+	}
+
+	if (type != FYTT_NONE)
+		goto do_token;
+
+again:
+
+	switch (fypp->expr_mode) {
+	case fyem_none:
+		assert(0);	/* should never happen */
+		break;
+
+	case fyem_path:
+
+		switch (c) {
+		case '/':
+			type = FYTT_PE_SLASH;
+			simple_token_count = 1;
+			break;
+
+		case '^':
+			type = FYTT_PE_ROOT;
+			simple_token_count = 1;
+			break;
+
+		case ':':
+			type = FYTT_PE_SIBLING;
+			simple_token_count = 1;
+			break;
+
+		case '$':
+			type = FYTT_PE_SCALAR_FILTER;
+			simple_token_count = 1;
+			break;
+
+		case '%':
+			type = FYTT_PE_COLLECTION_FILTER;
+			simple_token_count = 1;
+			break;
+
+		case '[':
+			if (fy_reader_peek_at(fyr, 1) == ']') {
+				type = FYTT_PE_SEQ_FILTER;
+				simple_token_count = 2;
+			}
+			break;
+
+		case '{':
+			if (fy_reader_peek_at(fyr, 1) == '}') {
+				type = FYTT_PE_MAP_FILTER;
+				simple_token_count = 2;
+			}
+			break;
+
+
+		case '.':
+			cn = fy_reader_peek_at(fyr, 1);
+			if (cn == '.') {
+				type = FYTT_PE_PARENT;
+				simple_token_count = 2;
+			} else if (!fy_is_first_alpha(cn)) {
+				type = FYTT_PE_THIS;
+				simple_token_count = 1;
+			}
+			break;
+
+		case '*':
+			if (fy_reader_peek_at(fyr, 1) == '*') {
+				type = FYTT_PE_EVERY_CHILD_R;
+				simple_token_count = 2;
+			} else if (!fy_is_first_alpha(fy_reader_peek_at(fyr, 1))) {
+				type = FYTT_PE_EVERY_CHILD;
+				simple_token_count = 1;
+			} else {
+				type = FYTT_PE_ALIAS;
+				simple_token_count = 2;
+				while (fy_is_alnum(fy_reader_peek_at(fyr, simple_token_count)))
+					simple_token_count++;
+			}
+			break;
+
+		case '!':
+			cn = fy_reader_peek_at(fyr, 1);
+			if (cn == '=') {
+				type = FYTT_PE_NOTEQ;
+				simple_token_count = 2;
+				break;
+			}
+			type = FYTT_PE_UNIQUE_FILTER;
+			simple_token_count = 1;
+			break;
+
+		default:
+			break;
+		}
+		break;
+
+	case fyem_scalar:
+
+
+		/* it is possible for the expression to be a path
+		 * we only detect a few cases (doing all too complex)
+		 * (/ , (./ , (*
+		 */
+		if (fy_token_type_can_be_path_expr(fypp->last_queued_token_type)) {
+			cn = fy_reader_peek_at(fyr, 1);
+			if (c == '/' ||
+			    (c == '.' && (cn == '/' || cn == ')' || cn == '>' || cn == '<' || cn == '!' || cn == '='))) {
+				fypp->expr_mode = fyem_path;
+#ifdef DEBUG_EXPR
+				fyr_notice(fyr, "switching to path expr\n");
+#endif
+				goto again;
+			}
+		}
+
+		switch (c) {
+		case '+':
+			type = FYTT_SE_PLUS;
+			simple_token_count = 1;
+			break;
+
+		case '-':
+			cn = fy_reader_peek_at(fyr, 1);
+			if (fy_is_num(cn) &&
+			    fy_token_type_can_be_before_negative_number(fypp->last_queued_token_type))
+				break;
+
+			type = FYTT_SE_MINUS;
+			simple_token_count = 1;
+			break;
+
+		case '*':
+			type = FYTT_SE_MULT;
+			simple_token_count = 1;
+			break;
+
+		case '/':
+			type = FYTT_SE_DIV;
+			simple_token_count = 1;
+			break;
+
+		default:
+			break;
+		}
+		break;
+	}
+
+do_token:
+	/* simple tokens */
+	if (simple_token_count > 0) {
+		fyt = fy_path_token_queue(fypp, type, fy_reader_fill_atom_a(fyr, simple_token_count));
+		fyr_error_check(fyr, fyt, err_out, "fy_path_token_queue() failed\n");
+
+		return 0;
+	}
+
+	switch (fypp->expr_mode) {
+	case fyem_none:
+		assert(0);	/* should never happen */
+		break;
+
+	case fyem_path:
+		if (fy_is_first_alpha(c))
+			return fy_path_fetch_plain_or_method(fypp, c, FYTT_PE_MAP_KEY, FYTT_PE_METHOD);
+
+		if (fy_is_path_flow_key_start(c))
+			return fy_path_fetch_flow_map_key(fypp, c);
+
+		if (fy_is_num(c) || (c == '-' && fy_is_num(fy_reader_peek_at(fyr, 1))))
+			return fy_path_fetch_seq_index_or_slice(fypp, c);
+
+		if (c == '.' && fy_is_first_alpha(fy_reader_peek_at(fyr, 1)))
+			return fy_path_fetch_dot_method(fypp, c, FYTT_PE_METHOD);
+
+		break;
+
+	case fyem_scalar:
+
+		if (fy_is_first_alpha(c))
+			return fy_path_fetch_plain_or_method(fypp, c, FYTT_SCALAR, FYTT_SE_METHOD);
+
+		if (fy_is_path_flow_scalar_start(c))
+			return fy_path_fetch_flow_scalar(fypp, c);
+
+		if (fy_is_num(c) || (c == '-' && fy_is_num(fy_reader_peek_at(fyr, 1))))
+			return fy_path_fetch_number(fypp, c);
+
+#if 0
+		if (c == '.' && fy_is_first_alpha(fy_reader_peek_at(fyr, 1)))
+			return fy_path_fetch_dot_method(fypp, c, FYTT_SE_METHOD);
+#endif
+
+		break;
+	}
+
+	FYR_PARSE_ERROR(fyr, 0, 1, FYEM_SCAN, "bad path expression starts here c=%d", c);
+
+err_out:
+	fypp->stream_error = true;
+	rc = -1;
+	return rc;
+}
+
+struct fy_token *fy_path_scan_peek(struct fy_path_parser *fypp, struct fy_token *fyt_prev)
+{
+	struct fy_token *fyt;
+	struct fy_reader *fyr;
+	int rc, last_token_activity_counter;
+
+	fyr = &fypp->reader;
+
+	/* nothing if stream end produced (and no stream end token in queue) */
+	if (!fyt_prev && fypp->stream_end_produced && fy_token_list_empty(&fypp->queued_tokens)) {
+
+		fyt = fy_token_list_head(&fypp->queued_tokens);
+		if (fyt && fyt->type == FYTT_STREAM_END)
+			return fyt;
+
+		return NULL;
+	}
+
+	for (;;) {
+		if (!fyt_prev)
+			fyt = fy_token_list_head(&fypp->queued_tokens);
+		else
+			fyt = fy_token_next(&fypp->queued_tokens, fyt_prev);
+		if (fyt)
+			break;
+
+		/* on stream error we're done */
+		if (fypp->stream_error)
+			return NULL;
+
+		/* keep track of token activity, if it didn't change
+		* after the fetch tokens call, the state machine is stuck
+		*/
+		last_token_activity_counter = fypp->token_activity_counter;
+
+		/* fetch more then */
+		rc = fy_path_fetch_tokens(fypp);
+		if (rc) {
+			fy_error(fypp->cfg.diag, "fy_path_fetch_tokens() failed\n");
+			goto err_out;
+		}
+		if (last_token_activity_counter == fypp->token_activity_counter) {
+			fy_error(fypp->cfg.diag, "out of tokens and failed to produce anymore");
+			goto err_out;
+		}
+	}
+
+	switch (fyt->type) {
+	case FYTT_STREAM_START:
+		fypp->stream_start_produced = true;
+		break;
+	case FYTT_STREAM_END:
+		fypp->stream_end_produced = true;
+
+		rc = fy_reader_input_done(fyr);
+		if (rc) {
+			fy_error(fypp->cfg.diag, "fy_parse_input_done() failed");
+			goto err_out;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return fyt;
+
+err_out:
+	fypp->stream_error = true;
+	return NULL;
+}
+
+struct fy_token *fy_path_scan_remove(struct fy_path_parser *fypp, struct fy_token *fyt)
+{
+	if (!fypp || !fyt)
+		return NULL;
+
+	fy_token_list_del(&fypp->queued_tokens, fyt);
+
+	return fyt;
+}
+
+struct fy_token *fy_path_scan_remove_peek(struct fy_path_parser *fypp, struct fy_token *fyt)
+{
+	fy_token_unref(fy_path_scan_remove(fypp, fyt));
+
+	return fy_path_scan_peek(fypp, NULL);
+}
+
+struct fy_token *fy_path_scan(struct fy_path_parser *fypp)
+{
+	return fy_path_scan_remove(fypp, fy_path_scan_peek(fypp, NULL));
+}
+
+void fy_path_expr_dump(struct fy_path_expr *expr, struct fy_diag *diag, enum fy_error_type errlevel, int level, const char *banner)
+{
+	struct fy_path_expr *expr2;
+	const char *style = "";
+	const char *text;
+	size_t len;
+	bool save_on_error;
+
+	if (errlevel < diag->cfg.level)
+		return;
+
+	save_on_error = diag->on_error;
+	diag->on_error = true;
+
+	if (banner)
+		fy_diag_diag(diag, errlevel, "%-*s%s", level*2, "", banner);
+
+	text = fy_token_get_text(expr->fyt, &len);
+
+	style = "";
+	if (expr->type == fpet_scalar) {
+		switch (fy_scalar_token_get_style(expr->fyt)) {
+		case FYSS_SINGLE_QUOTED:
+			style = "'";
+			break;
+		case FYSS_DOUBLE_QUOTED:
+			style = "\"";
+			break;
+		default:
+			style = "";
+			break;
+		}
+	}
+
+	fy_diag_diag(diag, errlevel, "> %-*s%s:%s %s%.*s%s",
+			level*2, "",
+			fy_path_expr_type_txt[expr->type],
+			fy_expr_mode_txt[expr->expr_mode],
+			style, (int)len, text, style);
+
+	for (expr2 = fy_path_expr_list_head(&expr->children); expr2; expr2 = fy_path_expr_next(&expr->children, expr2))
+		fy_path_expr_dump(expr2, diag, errlevel, level + 1, NULL);
+
+	diag->on_error = save_on_error;
+}
+
+static struct fy_node *
+fy_path_expr_to_node_internal(struct fy_document *fyd, struct fy_path_expr *expr)
+{
+	struct fy_path_expr *expr2;
+	const char *style = "";
+	const char *text;
+	size_t len;
+	struct fy_node *fyn = NULL, *fyn2, *fyn_seq = NULL;
+	int rc;
+
+	text = fy_token_get_text(expr->fyt, &len);
+
+	/* by default use double quoted style */
+	style = "\"";
+	switch (expr->type) {
+	case fpet_scalar:
+		switch (fy_scalar_token_get_style(expr->fyt)) {
+		case FYSS_SINGLE_QUOTED:
+			style = "'";
+			break;
+		case FYSS_DOUBLE_QUOTED:
+			style = "\"";
+			break;
+		default:
+			style = "";
+			break;
+		}
+		break;
+
+	case fpet_map_key:
+		/* no styles for complex map keys */
+		if (expr->fyt->map_key.fyd)
+			style = "";
+		break;
+
+	default:
+		break;
+	}
+
+	/* list is empty this is a terminal */
+	if (fy_path_expr_list_empty(&expr->children) &&
+	    expr->type != fpet_method) {
+
+		fyn = fy_node_buildf(fyd, "%s: %s%.*s%s",
+			fy_path_expr_type_txt[expr->type],
+			style, (int)len, text, style);
+		if (!fyn)
+			return NULL;
+
+		return fyn;
+	}
+
+	fyn = fy_node_create_mapping(fyd);
+	if (!fyn)
+		goto err_out;
+
+	fyn_seq = fy_node_create_sequence(fyd);
+	if (!fyn_seq)
+		goto err_out;
+
+	for (expr2 = fy_path_expr_list_head(&expr->children); expr2; expr2 = fy_path_expr_next(&expr->children, expr2)) {
+		fyn2 = fy_path_expr_to_node_internal(fyd, expr2);
+		if (!fyn2)
+			goto err_out;
+		rc = fy_node_sequence_append(fyn_seq, fyn2);
+		if (rc)
+			goto err_out;
+	}
+
+	if (expr->type != fpet_method) {
+		rc = fy_node_mapping_append(fyn,
+				fy_node_create_scalar(fyd, fy_path_expr_type_txt[expr->type], FY_NT),
+				fyn_seq);
+	} else {
+		rc = fy_node_mapping_append(fyn,
+				fy_node_create_scalarf(fyd, "%s()", expr->fym->name),
+				fyn_seq);
+	}
+	if (rc)
+		goto err_out;
+
+	return fyn;
+
+err_out:
+	fy_node_free(fyn_seq);
+	fy_node_free(fyn);
+	return NULL;
+}
+
+struct fy_document *fy_path_expr_to_document(struct fy_path_expr *expr)
+{
+	struct fy_document *fyd = NULL;
+
+	if (!expr)
+		return NULL;
+
+	fyd = fy_document_create(NULL);
+	if (!fyd)
+		return NULL;
+
+	fyd->root = fy_path_expr_to_node_internal(fyd, expr);
+	if (!fyd->root)
+		goto err_out;
+
+	return fyd;
+
+err_out:
+	fy_document_destroy(fyd);
+	return NULL;
+}
+
+enum fy_path_expr_type fy_map_token_to_path_expr_type(enum fy_token_type type, enum fy_expr_mode mode)
+{
+	switch (type) {
+	case FYTT_PE_ROOT:
+		return fpet_root;
+	case FYTT_PE_THIS:
+		return fpet_this;
+	case FYTT_PE_PARENT:
+	case FYTT_PE_SIBLING:	/* sibling maps to a chain of fpet_parent */
+		return fpet_parent;
+	case FYTT_PE_MAP_KEY:
+		return fpet_map_key;
+	case FYTT_PE_SEQ_INDEX:
+		return fpet_seq_index;
+	case FYTT_PE_SEQ_SLICE:
+		return fpet_seq_slice;
+	case FYTT_PE_EVERY_CHILD:
+		return fpet_every_child;
+	case FYTT_PE_EVERY_CHILD_R:
+		return fpet_every_child_r;
+	case FYTT_PE_ALIAS:
+		return fpet_alias;
+	case FYTT_PE_SCALAR_FILTER:
+		return fpet_filter_scalar;
+	case FYTT_PE_COLLECTION_FILTER:
+		return fpet_filter_collection;
+	case FYTT_PE_SEQ_FILTER:
+		return fpet_filter_sequence;
+	case FYTT_PE_MAP_FILTER:
+		return fpet_filter_mapping;
+	case FYTT_PE_UNIQUE_FILTER:
+		return fpet_filter_unique;
+	case FYTT_PE_COMMA:
+		return mode == fyem_path ? fpet_multi : fpet_arg_separator;
+	case FYTT_PE_SLASH:
+		return fpet_chain;
+	case FYTT_PE_BARBAR:
+		return fpet_logical_or;
+	case FYTT_PE_AMPAMP:
+		return fpet_logical_and;
+
+	case FYTT_PE_EQEQ:
+		return fpet_eq;
+	case FYTT_PE_NOTEQ:
+		return fpet_neq;
+	case FYTT_PE_LT:
+		return fpet_lt;
+	case FYTT_PE_GT:
+		return fpet_gt;
+	case FYTT_PE_LTE:
+		return fpet_lte;
+	case FYTT_PE_GTE:
+		return fpet_gte;
+
+	case FYTT_SCALAR:
+		return fpet_scalar;
+
+	case FYTT_SE_PLUS:
+		return fpet_plus;
+	case FYTT_SE_MINUS:
+		return fpet_minus;
+	case FYTT_SE_MULT:
+		return fpet_mult;
+	case FYTT_SE_DIV:
+		return fpet_div;
+
+	case FYTT_PE_LPAREN:
+		return fpet_lparen;
+	case FYTT_PE_RPAREN:
+		return fpet_rparen;
+
+	case FYTT_SE_METHOD:
+	case FYTT_PE_METHOD:
+		return fpet_method;
+
+	default:
+		/* note parentheses do not have an expression */
+		assert(0);
+		break;
+	}
+	return fpet_none;
+}
+
+bool fy_token_type_is_operand(enum fy_token_type type)
+{
+	return type == FYTT_PE_ROOT ||
+	       type == FYTT_PE_THIS ||
+	       type == FYTT_PE_PARENT ||
+	       type == FYTT_PE_MAP_KEY ||
+	       type == FYTT_PE_SEQ_INDEX ||
+	       type == FYTT_PE_SEQ_SLICE ||
+	       type == FYTT_PE_EVERY_CHILD ||
+	       type == FYTT_PE_EVERY_CHILD_R ||
+	       type == FYTT_PE_ALIAS ||
+
+	       type == FYTT_SCALAR;
+}
+
+bool fy_token_type_is_operator(enum fy_token_type type)
+{
+	return type == FYTT_PE_SLASH ||
+	       type == FYTT_PE_SCALAR_FILTER ||
+	       type == FYTT_PE_COLLECTION_FILTER ||
+	       type == FYTT_PE_SEQ_FILTER ||
+	       type == FYTT_PE_MAP_FILTER ||
+	       type == FYTT_PE_UNIQUE_FILTER ||
+	       type == FYTT_PE_SIBLING ||
+	       type == FYTT_PE_COMMA ||
+	       type == FYTT_PE_BARBAR ||
+	       type == FYTT_PE_AMPAMP ||
+	       type == FYTT_PE_LPAREN ||
+	       type == FYTT_PE_RPAREN ||
+
+	       type == FYTT_PE_EQEQ ||
+	       type == FYTT_PE_NOTEQ ||
+	       type == FYTT_PE_LT ||
+	       type == FYTT_PE_GT ||
+	       type == FYTT_PE_LTE ||
+	       type == FYTT_PE_GTE ||
+
+	       type == FYTT_SE_PLUS ||
+	       type == FYTT_SE_MINUS ||
+	       type == FYTT_SE_MULT ||
+	       type == FYTT_SE_DIV;
+}
+
+bool fy_token_type_is_operand_or_operator(enum fy_token_type type)
+{
+	return fy_token_type_is_operand(type) ||
+	       fy_token_type_is_operator(type);
+}
+
+int fy_path_expr_type_prec(enum fy_path_expr_type type)
+{
+	switch (type) {
+	default:
+		return -1;	/* terminals */
+	case fpet_filter_collection:
+	case fpet_filter_scalar:
+	case fpet_filter_sequence:
+	case fpet_filter_mapping:
+	case fpet_filter_unique:
+		return 5;
+	case fpet_logical_or:
+	case fpet_logical_and:
+		return 4;
+	case fpet_multi:
+		return 11;
+	case fpet_eq:
+	case fpet_neq:
+	case fpet_lt:
+	case fpet_gt:
+	case fpet_lte:
+	case fpet_gte:
+		return 7;
+	case fpet_mult:
+	case fpet_div:
+		return 9;
+	case fpet_plus:
+	case fpet_minus:
+		return 8;
+	case fpet_chain:
+		return 10;
+	case fpet_lparen:
+	case fpet_rparen:
+	case fpet_method:
+		return 1000;
+	case fpet_arg_separator:
+		return 1;	/* lowest */
+	}
+	return -1;
+}
+
+static inline FY_UNUSED void
+dump_operand_stack(struct fy_path_parser *fypp)
+{
+	return fy_expr_stack_dump(fypp->cfg.diag, &fypp->operands);
+}
+
+static inline int
+push_operand(struct fy_path_parser *fypp, struct fy_path_expr *expr)
+{
+	return fy_expr_stack_push(&fypp->operands, expr);
+}
+
+static inline FY_UNUSED struct fy_path_expr *
+peek_operand_at(struct fy_path_parser *fypp, unsigned int pos)
+{
+	return fy_expr_stack_peek_at(&fypp->operands, pos);
+}
+
+static inline FY_UNUSED struct fy_path_expr *
+peek_operand(struct fy_path_parser *fypp)
+{
+	return fy_expr_stack_peek(&fypp->operands);
+}
+
+static inline FY_UNUSED struct fy_path_expr *
+pop_operand(struct fy_path_parser *fypp)
+{
+	return fy_expr_stack_pop(&fypp->operands);
+}
+
+#define PREFIX	0
+#define INFIX	1
+#define SUFFIX	2
+
+int fy_token_type_operator_placement(enum fy_token_type type)
+{
+	switch (type) {
+	case FYTT_PE_SLASH:	/* SLASH is special at the start of the expression */
+	case FYTT_PE_COMMA:
+	case FYTT_PE_BARBAR:
+	case FYTT_PE_AMPAMP:
+	case FYTT_PE_EQEQ:
+	case FYTT_PE_NOTEQ:
+	case FYTT_PE_LT:
+	case FYTT_PE_GT:
+	case FYTT_PE_LTE:
+	case FYTT_PE_GTE:
+	case FYTT_SE_PLUS:
+	case FYTT_SE_MINUS:
+	case FYTT_SE_MULT:
+	case FYTT_SE_DIV:
+		return INFIX;
+	case FYTT_PE_SCALAR_FILTER:
+	case FYTT_PE_COLLECTION_FILTER:
+	case FYTT_PE_SEQ_FILTER:
+	case FYTT_PE_MAP_FILTER:
+	case FYTT_PE_UNIQUE_FILTER:
+		return SUFFIX;
+	case FYTT_PE_SIBLING:
+		return PREFIX;
+	default:
+		break;
+	}
+	return -1;
+}
+
+const struct fy_mark *fy_path_expr_start_mark(struct fy_path_expr *expr)
+{
+	if (!expr)
+		return NULL;
+
+	return fy_token_start_mark(expr->fyt);
+}
+
+const struct fy_mark *fy_path_expr_end_mark(struct fy_path_expr *expr)
+{
+	if (!expr)
+		return NULL;
+
+	return fy_token_end_mark(expr->fyt);
+}
+
+struct fy_token *
+expr_to_token_mark(struct fy_path_expr *expr, struct fy_input *fyi)
+{
+	const struct fy_mark *ms, *me;
+	struct fy_atom handle;
+
+	if (!expr || !fyi)
+		return NULL;
+
+	ms = fy_path_expr_start_mark(expr);
+	assert(ms);
+	me = fy_path_expr_end_mark(expr);
+	assert(me);
+
+	memset(&handle, 0, sizeof(handle));
+	handle.start_mark = *ms;
+	handle.end_mark = *me;
+	handle.fyi = fyi;
+	handle.style = FYAS_PLAIN;
+	handle.chomp = FYAC_CLIP;
+
+	return fy_token_create(FYTT_INPUT_MARKER, &handle);
+}
+
+struct fy_token *
+expr_lr_to_token_mark(struct fy_path_expr *exprl, struct fy_path_expr *exprr, struct fy_input *fyi)
+{
+	const struct fy_mark *ms, *me;
+	struct fy_atom handle;
+
+	if (!exprl || !exprr || !fyi)
+		return NULL;
+
+	ms = fy_path_expr_start_mark(exprl);
+	assert(ms);
+	me = fy_path_expr_end_mark(exprr);
+	assert(me);
+
+	memset(&handle, 0, sizeof(handle));
+	handle.start_mark = *ms;
+	handle.end_mark = *me;
+	handle.fyi = fyi;
+	handle.style = FYAS_PLAIN;
+	handle.chomp = FYAC_CLIP;
+
+	return fy_token_create(FYTT_INPUT_MARKER, &handle);
+}
+
+int
+fy_path_expr_order(struct fy_path_expr *expr1, struct fy_path_expr *expr2)
+{
+	const struct fy_mark *m1 = NULL, *m2 = NULL;
+
+	if (expr1)
+		m1 = fy_path_expr_start_mark(expr1);
+
+	if (expr2)
+		m2 = fy_path_expr_start_mark(expr2);
+
+	if (m1 == m2)
+		return 0;
+
+	if (!m1)
+		return -1;
+
+	if (!m2)
+		return 1;
+
+	return m1->input_pos == m2->input_pos ? 0 :
+	       m1->input_pos  < m2->input_pos ? -1 : 1;
+}
+
+int push_operand_lr(struct fy_path_parser *fypp,
+		    enum fy_path_expr_type type,
+		    struct fy_path_expr *exprl, struct fy_path_expr *exprr,
+		    bool optimize)
+{
+	struct fy_reader *fyr;
+	struct fy_path_expr *expr = NULL, *exprt;
+	const struct fy_mark *ms = NULL, *me = NULL;
+	struct fy_atom handle;
+	int ret;
+
+	optimize = false;
+	assert(exprl || exprr);
+
+	fyr = &fypp->reader;
+
+#if 0
+	fyr_notice(fyr, ">>> %s <%s> l=<%s> r=<%s>\n", __func__,
+			fy_path_expr_type_txt[type],
+			exprl ?fy_path_expr_type_txt[exprl->type] : "NULL",
+			exprr ?fy_path_expr_type_txt[exprr->type] : "NULL");
+#endif
+
+	expr = fy_path_expr_alloc_recycle(fypp);
+	fyr_error_check(fyr, expr, err_out,
+			"fy_path_expr_alloc_recycle() failed\n");
+
+	expr->type = type;
+	expr->fyt = NULL;
+
+	if (exprl) {
+		assert(exprl->fyt);
+		ms = fy_token_start_mark(exprl->fyt);
+		assert(ms);
+	} else {
+		ms = fy_token_start_mark(exprr->fyt);
+		assert(ms);
+	}
+
+	if (exprr) {
+		assert(exprr->fyt);
+		me = fy_token_end_mark(exprr->fyt);
+		assert(me);
+	} else {
+		me = fy_token_end_mark(exprr->fyt);
+		assert(me);
+	}
+
+	assert(ms && me);
+
+	memset(&handle, 0, sizeof(handle));
+	handle.start_mark = *ms;
+	handle.end_mark = *me;
+	handle.fyi = fypp->fyi;
+	handle.style = FYAS_PLAIN;
+	handle.chomp = FYAC_CLIP;
+
+	if (exprl) {
+		if (type == exprl->type && fy_path_expr_type_is_mergeable(type)) {
+			while ((exprt = fy_path_expr_list_pop(&exprl->children)) != NULL) {
+				fy_path_expr_list_add_tail(&expr->children, exprt);
+				exprt->parent = expr;
+			}
+			fy_path_expr_free_recycle(fypp, exprl);
+		} else {
+			fy_path_expr_list_add_tail(&expr->children, exprl);
+			exprl->parent = expr;
+		}
+		exprl = NULL;
+	}
+
+	if (exprr) {
+		if (type == exprr->type && fy_path_expr_type_is_mergeable(type)) {
+			while ((exprt = fy_path_expr_list_pop(&exprr->children)) != NULL) {
+				fy_path_expr_list_add_tail(&expr->children, exprt);
+				exprt->parent = expr;
+			}
+			fy_path_expr_free_recycle(fypp, exprr);
+		} else {
+			fy_path_expr_list_add_tail(&expr->children, exprr);
+			exprr->parent = expr;
+		}
+		exprr = NULL;
+	}
+
+	expr->fyt = fy_token_create(FYTT_INPUT_MARKER, &handle);
+	fyr_error_check(fyr, expr->fyt, err_out,
+			"expr_to_token_mark() failed\n");
+
+	ret = push_operand(fypp, expr);
+	fyr_error_check(fyr, !ret, err_out,
+			"push_operand() failed\n");
+
+#ifdef DEBUG_EXPR
+	FYR_TOKEN_DIAG(fyr, expr->fyt,
+		FYDF_NOTICE, FYEM_PARSE, "pushed operand lr");
+#endif
+
+	return 0;
+err_out:
+	fy_path_expr_free(expr);
+	fy_path_expr_free(exprl);
+	fy_path_expr_free(exprr);
+	return -1;
+}
+
+enum fy_method_idx {
+	fymi_test,
+	fymi_sum,
+	fymi_this,
+	fymi_parent,
+	fymi_root,
+	fymi_any,
+	fymi_all,
+	fymi_select,
+	fymi_key,
+	fymi_value,
+	fymi_index,
+	fymi_null,
+};
+
+static struct fy_walk_result *
+common_builtin_ref_exec(const struct fy_method *fym,
+	struct fy_path_exec *fypx, int level,
+	struct fy_path_expr *expr,
+	struct fy_walk_result *input,
+	struct fy_walk_result **args, int nargs);
+
+static struct fy_walk_result *
+common_builtin_collection_exec(const struct fy_method *fym,
+	struct fy_path_exec *fypx, int level,
+	struct fy_path_expr *expr,
+	struct fy_walk_result *input,
+	struct fy_walk_result **args, int nargs);
+
+
+static struct fy_walk_result *
+test_exec(const struct fy_method *fym,
+	  struct fy_path_exec *fypx, int level,
+	  struct fy_path_expr *expr,
+	  struct fy_walk_result *input,
+	  struct fy_walk_result **args, int nargs);
+
+static struct fy_walk_result *
+sum_exec(const struct fy_method *fym,
+	 struct fy_path_exec *fypx, int level,
+	 struct fy_path_expr *expr,
+	 struct fy_walk_result *input,
+	 struct fy_walk_result **args, int nargs);
+
+static const struct fy_method fy_methods[] = {
+	[fymi_test] = {
+		.name	= "test",
+		.len    = 4,
+		.mode	= fyem_scalar,
+		.nargs	= 1,
+		.exec	= test_exec,
+	},
+	[fymi_sum] = {
+		.name	= "sum",
+		.len    = 3,
+		.mode	= fyem_scalar,
+		.nargs	= 2,
+		.exec	= sum_exec,
+	},
+	[fymi_this] = {
+		.name	= "this",
+		.len    = 4,
+		.mode	= fyem_path,
+		.nargs	= 0,
+		.exec	= common_builtin_ref_exec,
+	},
+	[fymi_parent] = {
+		.name	= "parent",
+		.len    = 6,
+		.mode	= fyem_path,
+		.nargs	= 0,
+		.exec	= common_builtin_ref_exec,
+	},
+	[fymi_root] = {
+		.name	= "root",
+		.len    = 4,
+		.mode	= fyem_path,
+		.nargs	= 0,
+		.exec	= common_builtin_ref_exec,
+	},
+	[fymi_any] = {
+		.name	= "any",
+		.len    = 3,
+		.mode	= fyem_path,
+		.nargs	= 1,
+		.exec	= common_builtin_collection_exec,
+	},
+	[fymi_all] = {
+		.name	= "all",
+		.len    = 3,
+		.mode	= fyem_path,
+		.nargs	= 1,
+		.exec	= common_builtin_collection_exec,
+	},
+	[fymi_select] = {
+		.name	= "select",
+		.len    = 6,
+		.mode	= fyem_path,
+		.nargs	= 1,
+		.exec	= common_builtin_collection_exec,
+	},
+	[fymi_key] = {
+		.name	= "key",
+		.len    = 3,
+		.mode	= fyem_path,
+		.nargs	= 1,
+		.exec	= common_builtin_ref_exec,
+	},
+	[fymi_value] = {
+		.name	= "value",
+		.len    = 5,
+		.mode	= fyem_path,
+		.nargs	= 1,
+		.exec	= common_builtin_ref_exec,
+	},
+	[fymi_index] = {
+		.name	= "index",
+		.len    = 5,
+		.mode	= fyem_path,
+		.nargs	= 1,
+		.exec	= common_builtin_ref_exec,
+	},
+	[fymi_null] = {
+		.name	= "null",
+		.len    = 4,
+		.mode	= fyem_path,
+		.nargs	= 0,
+		.exec	= common_builtin_ref_exec,
+	},
+};
+
+static inline int fy_method_to_builtin_idx(const struct fy_method *fym)
+{
+	if (!fym || fym < fy_methods || fym >= &fy_methods[ARRAY_SIZE(fy_methods)])
+		return -1;
+	return fym - fy_methods;
+}
+
+static struct fy_walk_result *
+common_builtin_ref_exec(const struct fy_method *fym,
+	    struct fy_path_exec *fypx, int level,
+            struct fy_path_expr *expr,
+	    struct fy_walk_result *input,
+	    struct fy_walk_result **args, int nargs)
+{
+	enum fy_method_idx midx;
+	struct fy_walk_result *output = NULL;
+	struct fy_walk_result *fwr, *fwrn;
+	struct fy_node *fyn, *fynt;
+	int i;
+
+	if (!fypx || !input)
+		goto out;
+
+	i = fy_method_to_builtin_idx(fym);
+	if (i < 0)
+		goto out;
+	midx = (enum fy_method_idx)i;
+
+	switch (midx) {
+	case fymi_key:
+	case fymi_value:
+		if (!args || nargs != 1 || !args[0] || args[0]->type != fwrt_string)
+			goto out;
+		break;
+	case fymi_index:
+		if (!args || nargs != 1 || !args[0] || args[0]->type != fwrt_number)
+			goto out;
+		break;
+	case fymi_root:
+	case fymi_parent:
+	case fymi_this:
+	case fymi_null:
+		if (nargs != 0)
+			goto out;
+		break;
+	default:
+		goto out;
+	}
+
+	output = fy_path_exec_walk_result_create(fypx, fwrt_refs);
+	assert(output);
+
+	for (fwr = fy_walk_result_iter_start(input); fwr;
+			fwr = fy_walk_result_iter_next(input, fwr)) {
+
+		if (fwr->type != fwrt_node_ref || !fwr->fyn)
+			continue;
+
+		fynt = fwr->fyn;
+
+		switch (midx) {
+		case fymi_key:
+		case fymi_value:
+		case fymi_index:
+		case fymi_this:
+		case fymi_null:
+			/* dereference alias */
+			if (fy_node_is_alias(fynt)) {
+				// fprintf(stderr, "%s: %s calling fy_node_alias_resolve_by_ypath()\n", __func__, fy_node_get_path_alloca(fyn));
+				fynt = fy_node_alias_resolve_by_ypath(fynt);
+			}
+			break;
+		default:
+			break;
+		}
+
+		fyn = NULL;
+		switch (midx) {
+		case fymi_key:
+			if (!fy_node_is_mapping(fynt))
+				break;
+			fyn = fy_node_mapping_lookup_key_by_string(fynt, args[0]->string, FY_NT);
+			break;
+
+		case fymi_value:
+			if (!fy_node_is_mapping(fynt))
+				break;
+			fyn = fy_node_mapping_lookup_by_string(fynt, args[0]->string, FY_NT);
+			break;
+
+		case fymi_index:
+			if (!fy_node_is_sequence(fynt))
+				break;
+			fyn = fy_node_sequence_get_by_index(fynt, (int)args[0]->number);
+			break;
+
+		case fymi_root:
+			fyn = fy_document_root(fy_node_document(fynt));
+			break;
+
+		case fymi_parent:
+			fyn = fy_node_get_parent(fynt);
+			break;
+
+		case fymi_null:
+			if (!fy_node_is_mapping(fynt))
+				break;
+			fyn = fy_node_mapping_lookup_value_by_null_key(fynt);
+			break;
+
+		case fymi_this:
+			fyn = fynt;
+			break;
+
+		default:
+			break;
+		}
+
+		if (!fyn)
+			continue;
+
+		fwrn = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fyn);
+		assert(fwrn);
+
+		fy_walk_result_list_add_tail(&output->refs, fwrn);
+	}
+
+	/* output convert zero to NULL, singular to node_ref */
+	if (output && output->type == fwrt_refs) {
+		if (fy_walk_result_list_empty(&output->refs)) {
+			fy_walk_result_free(output);
+			output = NULL;
+		} else if (fy_walk_result_list_is_singular(&output->refs)) {
+			fwr = fy_walk_result_list_pop(&output->refs);
+			assert(fwr);
+			fy_walk_result_free(output);
+			output = fwr;
+		}
+	}
+
+out:
+	fy_walk_result_free(input);
+	if (args) {
+		for (i = 0; i < nargs; i++)
+			fy_walk_result_free(args[i]);
+	}
+	return output;
+}
+
+static struct fy_walk_result *
+common_builtin_collection_exec(const struct fy_method *fym,
+	 struct fy_path_exec *fypx, int level,
+	 struct fy_path_expr *expr,
+	 struct fy_walk_result *input,
+	 struct fy_walk_result **args, int nargs)
+{
+	enum fy_method_idx midx;
+	struct fy_walk_result *output = NULL;
+	struct fy_walk_result *fwr, *fwrn, *fwrt;
+	struct fy_path_expr *expr_arg;
+	bool match, done;
+	int input_count, match_count;
+	int i;
+
+	if (!fypx || !input)
+		goto out;
+
+	i = fy_method_to_builtin_idx(fym);
+	if (i < 0)
+		goto out;
+	midx = (enum fy_method_idx)i;
+
+	switch (midx) {
+	case fymi_any:
+	case fymi_all:
+	case fymi_select:
+		if (!args || nargs != 1 || !args[0])
+			goto out;
+		break;
+	default:
+		goto out;
+	}
+
+	expr_arg = fy_path_expr_list_head(&expr->children);
+	assert(expr_arg);
+
+	/* only handle inputs of node and refs */
+	if (input->type != fwrt_node_ref && input->type != fwrt_refs)
+		goto out;
+
+	output = NULL;
+
+	switch (midx) {
+	case fymi_select:
+		output = fy_path_exec_walk_result_create(fypx, fwrt_refs);
+		assert(output);
+		break;
+	default:
+		break;
+	}
+
+
+	done = false;
+	match_count = input_count = 0;
+	for (fwr = fy_walk_result_iter_start(input); fwr && !done; fwr = fy_walk_result_iter_next(input, fwr)) {
+
+		input_count++;
+
+		fwrt = fy_walk_result_clone(fwr);
+		assert(fwrt);
+
+		fwrn = fy_path_expr_execute(fypx, level + 1, expr_arg, fwrt, expr->type);
+
+		match = fwrn != NULL;
+		if (match)
+			match_count++;
+
+		switch (midx) {
+		case fymi_any:
+			/* on any match, we're done */
+			if (match)
+				done = true;
+			break;
+
+		case fymi_all:
+			/* on any non match, we're done */
+			if (!match)
+				done = true;
+			break;
+
+		case fymi_select:
+			/* select only works on node refs */
+			if (fwr->type != fwrt_node_ref)
+				break;
+			if (match) {
+				fwrt = fy_walk_result_clone(fwr);
+				assert(fwrt);
+				fy_walk_result_list_add_tail(&output->refs, fwrt);
+			}
+			break;
+
+		default:
+			break;
+		}
+
+		if (fwrn)
+			fy_walk_result_free(fwrn);
+	}
+
+	switch (midx) {
+	case fymi_any:
+		if (input_count > 0 && match_count <= input_count) {
+			output = input;
+			input = NULL;
+		}
+		break;
+	case fymi_all:
+		if (input_count > 0 && match_count == input_count) {
+			output = input;
+			input = NULL;
+		}
+		break;
+
+	default:
+		break;
+	}
+
+	/* output convert zero to NULL, singular to node_ref */
+	if (output && output->type == fwrt_refs) {
+		if (fy_walk_result_list_empty(&output->refs)) {
+			fy_walk_result_free(output);
+			output = NULL;
+		} else if (fy_walk_result_list_is_singular(&output->refs)) {
+			fwr = fy_walk_result_list_pop(&output->refs);
+			assert(fwr);
+			fy_walk_result_free(output);
+			output = fwr;
+		}
+	}
+
+out:
+	if (input)
+		fy_walk_result_free(input);
+	if (args) {
+		for (i = 0; i < nargs; i++)
+			fy_walk_result_free(args[i]);
+	}
+
+	return output;
+}
+
+static struct fy_walk_result *
+test_exec(const struct fy_method *fym,
+	  struct fy_path_exec *fypx, int level,
+	  struct fy_path_expr *expr,
+	  struct fy_walk_result *input,
+	  struct fy_walk_result **args, int nargs)
+{
+	int i;
+	struct fy_walk_result *output = NULL;
+
+	if (!fypx || !args || nargs != 1)
+		goto out;
+
+	/* require a single number argument */
+	if (!args[0] || args[0]->type != fwrt_number)
+		goto out;
+
+	/* reuse argument */
+	output = args[0];
+	args[0] = NULL;
+
+	/* add 1 to the number */
+	output->number += 1;
+
+out:
+	fy_walk_result_free(input);
+	if (args) {
+		for (i = 0; i < nargs; i++)
+			fy_walk_result_free(args[i]);
+	}
+	return output;
+}
+
+static struct fy_walk_result *
+sum_exec(const struct fy_method *fym,
+	 struct fy_path_exec *fypx, int level,
+         struct fy_path_expr *expr,
+	 struct fy_walk_result *input,
+	 struct fy_walk_result **args, int nargs)
+{
+	int i;
+	struct fy_walk_result *output = NULL;
+
+	if (!fypx || !args || nargs != 2)
+		goto out;
+
+	/* require two number argument */
+	if (!args[0] || args[0]->type != fwrt_number ||
+	    !args[1] || args[1]->type != fwrt_number)
+		goto out;
+
+	/* reuse argument */
+	output = args[0];
+	args[0] = NULL;
+
+	/* add 1 to the number */
+	output->number += args[1]->number;
+
+out:
+	fy_walk_result_free(input);
+	if (args) {
+		for (i = 0; i < nargs; i++)
+			fy_walk_result_free(args[i]);
+	}
+	return output;
+}
+
+int evaluate_method(struct fy_path_parser *fypp, struct fy_path_expr *exprm,
+		    struct fy_path_expr *exprl, struct fy_path_expr *exprr)
+{
+	struct fy_reader *fyr;
+	struct fy_path_expr *exprt;
+	struct fy_token *fyt;
+	const char *text;
+	size_t len;
+	const struct fy_method *fym;
+	unsigned int i, count;
+	int ret;
+
+	fyr = &fypp->reader;
+
+#ifdef DEBUG_EXPR
+	FYR_TOKEN_DIAG(fyr, exprm->fyt,
+		FYDF_NOTICE, FYEM_PARSE, "evaluating method");
+#endif
+
+	text = fy_token_get_text(exprm->fyt, &len);
+	fyr_error_check(fyr, text, err_out,
+			"fy_token_get_text() failed\n");
+
+	for (i = 0, fym = fy_methods; i < ARRAY_SIZE(fy_methods); i++, fym++) {
+		if (fym->len == len && !memcmp(text, fym->name, len))
+			break;
+	}
+
+	FYR_TOKEN_ERROR_CHECK(fyr, exprm->fyt, FYEM_PARSE,
+			i < ARRAY_SIZE(fy_methods), err_out,
+			"invalid method %.*s\n", (int)len, text);
+
+	/* reuse exprm */
+	count = 0;
+	while ((exprt = fy_expr_stack_peek(&fypp->operands)) != NULL &&
+		fy_path_expr_order(exprm, exprt) < 0) {
+
+		exprt = fy_expr_stack_pop(&fypp->operands);
+		assert(exprt);
+
+#ifdef DEBUG_EXPR
+		FYR_TOKEN_DIAG(fyr, exprt->fyt,
+			FYDF_NOTICE, FYEM_PARSE, "poped argument %d", count);
+#endif
+
+		/* add in reverse order */
+		fy_path_expr_list_add(&exprm->children, exprt);
+		exprt->parent = exprm;
+		count++;
+
+	}
+
+	if (exprr) {
+		fyt = expr_lr_to_token_mark(exprm, exprr, fypp->fyi);
+		fyr_error_check(fyr, fyt, err_out,
+				"expr_lr_to_token_mark() failed\n");
+
+		fy_token_unref(exprm->fyt);
+		exprm->fyt = fyt;
+	}
+
+	FYR_TOKEN_ERROR_CHECK(fyr, exprm->fyt, FYEM_PARSE,
+			fym->nargs == count, err_out,
+			"too %s argument for method %s, expected %d, got %d\n",
+			fym->nargs < count ? "many" : "few",
+			fym->name, fym->nargs, count);
+
+	exprm->fym = fym;
+
+	if (exprl)
+		fy_path_expr_free_recycle(fypp, exprl);
+	if (exprr)
+		fy_path_expr_free_recycle(fypp, exprr);
+
+	/* and push as an operand */
+	ret = push_operand(fypp, exprm);
+	fyr_error_check(fyr, !ret, err_out,
+			"push_operand() failed\n");
+
+#ifdef DEBUG_EXPR
+	FYR_TOKEN_DIAG(fyr, exprm->fyt,
+		FYDF_NOTICE, FYEM_PARSE, "pushed operand evaluate_method");
+#endif
+	return 0;
+
+err_out:
+	/* we don't need the parentheses operators */
+	fy_path_expr_free_recycle(fypp, exprm);
+	if (exprl)
+		fy_path_expr_free_recycle(fypp, exprl);
+	if (exprr)
+		fy_path_expr_free_recycle(fypp, exprr);
+
+	return -1;
+}
+
+int evaluate_new(struct fy_path_parser *fypp)
+{
+	struct fy_reader *fyr;
+	struct fy_path_expr *expr = NULL, *expr_peek, *exprt;
+	struct fy_path_expr *exprl = NULL, *exprr = NULL, *chain = NULL, *exprm = NULL;
+	struct fy_path_expr *parent = NULL;
+	struct fy_token *fyt;
+	enum fy_path_expr_type type, etype;
+	int ret;
+
+	fyr = &fypp->reader;
+
+	expr = fy_expr_stack_pop(&fypp->operators);
+	fyr_error_check(fyr, expr, err_out,
+			"pop_operator() failed to find token operator to evaluate\n");
+
+	assert(expr->fyt);
+
+#ifdef DEBUG_EXPR
+	FYR_TOKEN_DIAG(fyr, expr->fyt,
+		FYDF_NOTICE, FYEM_PARSE, "poped operator expression");
+#endif
+
+	exprl = NULL;
+	exprr = NULL;
+	type = expr->type;
+	switch (type) {
+
+	case fpet_chain:
+
+		/* dump_operand_stack(fypp); */
+		/* dump_operator_stack(fypp); */
+
+		/* peek the next operator */
+		expr_peek = fy_expr_stack_peek(&fypp->operators);
+
+		/* pop the top in either case */
+		exprr = fy_expr_stack_pop(&fypp->operands);
+		if (!exprr) {
+			// fyr_notice(fyr, "ROOT value (with no arguments)\n");
+
+			/* conver to root and push to operands */
+			expr->type = fpet_root;
+
+			ret = push_operand(fypp, expr);
+			fyr_error_check(fyr, !ret, err_out,
+					"push_operand() failed\n");
+			return 0;
+		}
+
+#ifdef DEBUG_EXPR
+		FYR_TOKEN_DIAG(fyr, exprr->fyt,
+			FYDF_NOTICE, FYEM_PARSE, "exprr");
+#endif
+
+		/* expression is to the left, that means it's a root chain */
+		if (fy_path_expr_order(expr, exprr) < 0 &&
+		    (!(exprl = fy_expr_stack_peek(&fypp->operands)) ||
+		     (expr_peek && fy_path_expr_order(exprl, expr_peek) <= 0))) {
+
+			// fyr_notice(fyr, "ROOT operator (with arguments)\n");
+
+			exprl = fy_path_expr_alloc_recycle(fypp);
+			fyr_error_check(fyr, exprl, err_out,
+					"fy_path_expr_alloc_recycle() failed\n");
+			exprl->type = fpet_root;
+
+			/* move token to the root */
+			exprl->fyt = expr->fyt;
+			expr->fyt = NULL;
+
+		} else if (!(exprl = fy_expr_stack_pop(&fypp->operands))) {
+
+			// fyr_notice(fyr, "COLLECTION operator\n");
+
+			exprl = exprr;
+
+			exprr = fy_path_expr_alloc_recycle(fypp);
+			fyr_error_check(fyr, exprr, err_out,
+					"fy_path_expr_alloc_recycle() failed\n");
+			exprr->type = fpet_filter_collection;
+
+			/* move token to the filter collection */
+			exprr->fyt = expr->fyt;
+			expr->fyt = NULL;
+
+		} else {
+			assert(exprr && exprl);
+
+			// fyr_notice(fyr, "CHAIN operator\n");
+		}
+
+		/* we don't need the chain operator now */
+		fy_path_expr_free_recycle(fypp, expr);
+		expr = NULL;
+
+		ret = push_operand_lr(fypp, fpet_chain, exprl, exprr, true);
+		fyr_error_check(fyr, !ret, err_out,
+				"push_operand_lr() failed\n");
+		return 0;
+
+	case fpet_multi:
+	case fpet_logical_or:
+	case fpet_logical_and:
+
+	case fpet_eq:
+	case fpet_neq:
+	case fpet_lt:
+	case fpet_gt:
+	case fpet_lte:
+	case fpet_gte:
+
+	case fpet_plus:
+	case fpet_minus:
+	case fpet_mult:
+	case fpet_div:
+
+		exprl = NULL;
+		exprr = NULL;
+		exprt = fy_expr_stack_peek(&fypp->operators);
+
+		// fyr_error(fyr, "mode=%s top-mode=%s\n",
+		//		fy_expr_mode_txt[fypp->expr_mode],
+		//		exprt ? fy_expr_mode_txt[exprt->expr_mode] : "");
+
+#if 0
+		exprr = fy_expr_stack_peek(&fypp->operands);
+		if (exprr && exprt && fy_path_expr_order(exprr, exprt) <= 0)
+			exprr = NULL;
+		else
+#endif
+			exprr = fy_expr_stack_pop(&fypp->operands);
+		fyr_error_check(fyr, exprr, err_out,
+				"fy_expr_stack_pop() failed for exprr\n");
+
+#if 0
+		exprl = fy_expr_stack_peek_at(&fypp->operands, 1);
+		if (exprl && exprt && fy_path_expr_order(exprl, exprt) <= 0)
+			exprl = NULL;
+		else
+#endif
+			exprl = fy_expr_stack_pop(&fypp->operands);
+		fyr_error_check(fyr, exprl, err_out,
+				"fy_expr_stack_pop() failed for exprl\n");
+
+		/* we don't need the operator now */
+		fy_path_expr_free_recycle(fypp, expr);
+		expr = NULL;
+
+		ret = push_operand_lr(fypp, type, exprl, exprr, true);
+		fyr_error_check(fyr, !ret, err_out,
+				"push_operand_lr() failed\n");
+
+		break;
+
+	case fpet_filter_collection:
+	case fpet_filter_scalar:
+	case fpet_filter_sequence:
+	case fpet_filter_mapping:
+	case fpet_filter_unique:
+
+		exprl = fy_expr_stack_pop(&fypp->operands);
+		FYR_TOKEN_ERROR_CHECK(fyr, expr->fyt, FYEM_PARSE,
+				exprl, err_out,
+				"filter operator without argument");
+
+		exprr = fy_path_expr_alloc_recycle(fypp);
+		fyr_error_check(fyr, exprr, err_out,
+				"fy_path_expr_alloc_recycle() failed\n");
+		exprr->type = type;
+
+		/* move token to the filter collection */
+		exprr->fyt = expr->fyt;
+		expr->fyt = NULL;
+
+		/* we don't need the operator now */
+		fy_path_expr_free_recycle(fypp, expr);
+		expr = NULL;
+
+		/* push as a chain */
+		ret = push_operand_lr(fypp, fpet_chain, exprl, exprr, true);
+		fyr_error_check(fyr, !ret, err_out,
+				"push_operand_lr() failed\n");
+
+		break;
+
+	case fpet_lparen:
+		abort();
+		assert(0);
+
+#ifdef DEBUG_EXPR
+		FYR_TOKEN_DIAG(fyr, expr->fyt,
+			FYDF_NOTICE, FYEM_PARSE, "(");
+#endif
+
+		return 0;
+
+	case fpet_arg_separator:
+
+		/* separator is right hand side of the expression now */
+		exprr = expr;
+		expr = NULL;
+
+		/* evaluate until we hit a match to the rparen */
+		exprl = fy_expr_stack_peek(&fypp->operators);
+
+		if (!fy_path_expr_type_is_lparen(exprl->type)) {
+			ret = evaluate_new(fypp);
+			if (ret)
+				goto err_out;
+		}
+		exprl = NULL;
+
+		fy_path_expr_free_recycle(fypp, exprr);
+		exprr = NULL;
+
+		break;
+
+	case fpet_rparen:
+
+		/* rparen is right hand side of the expression now */
+		exprr = expr;
+		expr = NULL;
+
+		/* evaluate until we hit a match to the rparen */
+		while ((exprl = fy_expr_stack_peek(&fypp->operators)) != NULL) {
+
+			if (fy_path_expr_type_is_lparen(exprl->type))
+				break;
+
+			ret = evaluate_new(fypp);
+			if (ret)
+				goto err_out;
+		}
+
+		FYR_TOKEN_ERROR_CHECK(fyr, exprr->fyt, FYEM_PARSE,
+				exprl, err_out,
+				"missing matching left parentheses");
+
+		exprl = fy_expr_stack_pop(&fypp->operators);
+		assert(exprl);
+
+		exprt = fy_expr_stack_peek(&fypp->operands);
+
+		etype = exprl->expr_mode == fyem_scalar ? fpet_scalar_expr : fpet_path_expr;
+
+		/* already is an expression, reuse */
+		if (exprt && exprt->type == etype) {
+
+			fyt = expr_lr_to_token_mark(exprl, exprr, fypp->fyi);
+			fyr_error_check(fyr, fyt, err_out,
+					"expr_lr_to_token_mark() failed\n");
+			fy_token_unref(exprt->fyt);
+			exprt->fyt = fyt;
+			exprt->expr_mode = exprl->expr_mode;
+
+			/* we don't need the parentheses operators */
+			fy_path_expr_free_recycle(fypp, exprl);
+			exprl = NULL;
+			fy_path_expr_free_recycle(fypp, exprr);
+			exprr = NULL;
+
+			return 0;
+		}
+
+		/* if it's method, evaluate */
+		exprm = fy_expr_stack_peek(&fypp->operators);
+		if (exprm && exprm->type == fpet_method) {
+
+			exprm = fy_expr_stack_pop(&fypp->operators);
+			assert(exprm);
+
+			return evaluate_method(fypp, exprm, exprl, exprr);
+		}
+
+		expr = fy_path_expr_alloc_recycle(fypp);
+		fyr_error_check(fyr, expr, err_out,
+				"fy_path_expr_alloc_recycle() failed\n");
+		expr->type = etype;
+		expr->expr_mode = exprl->expr_mode;
+
+		expr->fyt = expr_lr_to_token_mark(exprl, exprr, fypp->fyi);
+
+		exprt = fy_expr_stack_pop(&fypp->operands);
+
+		FYR_TOKEN_ERROR_CHECK(fyr, exprr->fyt, FYEM_PARSE,
+				exprt, err_out,
+				"empty expression in parentheses");
+
+		fy_path_expr_list_add_tail(&expr->children, exprt);
+		exprt->parent = expr;
+
+		/* pop all operands that after exprl */
+		while ((exprt = fy_expr_stack_peek(&fypp->operands)) != NULL &&
+			fy_path_expr_order(exprt, exprl) >= 0) {
+#ifdef DEBUG_EXPR
+			FYR_TOKEN_DIAG(fyr, exprt->fyt,
+				FYDF_NOTICE, FYEM_PARSE, "discarding argument");
+#endif
+			fy_path_expr_free_recycle(fypp, fy_expr_stack_pop(&fypp->operands));
+		}
+
+		if (exprl->expr_mode != fyem_none) {
+			fypp->expr_mode = exprl->expr_mode;
+#ifdef DEBUG_EXPR
+			fyr_notice(fyr, "poping expr_mode %s\n", fy_expr_mode_txt[fypp->expr_mode]);
+#endif
+		}
+
+		/* we don't need the parentheses operators */
+		fy_path_expr_free_recycle(fypp, exprl);
+		exprl = NULL;
+		fy_path_expr_free_recycle(fypp, exprr);
+		exprr = NULL;
+
+		ret = push_operand(fypp, expr);
+		fyr_error_check(fyr, !ret, err_out,
+				"push_operand() failed\n");
+
+#ifdef DEBUG_EXPR
+		FYR_TOKEN_DIAG(fyr, expr->fyt,
+			FYDF_NOTICE, FYEM_PARSE, "pushed operand evaluate_new");
+#endif
+		return 0;
+
+	case fpet_method:
+		return evaluate_method(fypp, expr, NULL, NULL);
+
+		/* shoud never */
+	case fpet_scalar_expr:
+	case fpet_path_expr:
+		assert(0);
+		abort();
+
+	default:
+		fyr_error(fyr, "Unknown expression %s\n", fy_path_expr_type_txt[expr->type]);
+		goto err_out;
+	}
+
+	return 0;
+
+err_out:
+
+#ifdef DEBUG_EXPR
+	if (expr)
+		fy_path_expr_dump(expr, fypp->cfg.diag, FYET_NOTICE, 0, "expr:");
+	if (exprl)
+		fy_path_expr_dump(exprl, fypp->cfg.diag, FYET_NOTICE, 0, "exprl:");
+	if (exprr)
+		fy_path_expr_dump(exprr, fypp->cfg.diag, FYET_NOTICE, 0, "exprr:");
+	if (chain)
+		fy_path_expr_dump(chain, fypp->cfg.diag, FYET_NOTICE, 0, "chain:");
+	if (parent)
+		fy_path_expr_dump(parent, fypp->cfg.diag, FYET_NOTICE, 0, "parent:");
+
+	fy_notice(fypp->cfg.diag, "operator stack\n");
+	fy_expr_stack_dump(fypp->cfg.diag, &fypp->operators);
+	fy_notice(fypp->cfg.diag, "operand stack\n");
+	fy_expr_stack_dump(fypp->cfg.diag, &fypp->operands);
+#endif
+
+	fy_path_expr_free(expr);
+	fy_path_expr_free(exprl);
+	fy_path_expr_free(exprr);
+	fy_path_expr_free(chain);
+	fy_path_expr_free(parent);
+
+	return -1;
+}
+
+int fy_path_check_expression_alias(struct fy_path_parser *fypp, struct fy_path_expr *expr)
+{
+	struct fy_reader *fyr;
+	struct fy_path_expr *exprn;
+	int rc;
+
+	if (!expr)
+		return 0;
+
+	fyr = &fypp->reader;
+
+	/* an alias with a parent.. must be the first one */
+	if (expr->type == fpet_alias && expr->parent) {
+
+		exprn = fy_path_expr_list_head(&expr->parent->children);
+
+		/* an alias may only be the first of a path expression */
+		FYR_TOKEN_ERROR_CHECK(fyr, expr->fyt, FYEM_PARSE,
+				expr == exprn, err_out,
+				"alias is not first in the path expresion");
+	}
+
+	for (exprn = fy_path_expr_list_head(&expr->children); exprn;
+		exprn = fy_path_expr_next(&expr->children, exprn)) {
+
+		rc = fy_path_check_expression_alias(fypp, exprn);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+
+err_out:
+	return -1;
+}
+
+/* check expression for validity */
+int fy_path_check_expression(struct fy_path_parser *fypp, struct fy_path_expr *expr)
+{
+	int rc;
+
+	rc = fy_path_check_expression_alias(fypp, expr);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
+struct fy_path_expr *
+fy_path_parse_expression(struct fy_path_parser *fypp)
+{
+	struct fy_reader *fyr;
+	struct fy_token *fyt = NULL;
+	enum fy_token_type fytt;
+	struct fy_path_expr *expr, *expr_top, *exprt;
+	enum fy_expr_mode old_scan_mode, prev_scan_mode;
+	int ret, rc;
+#ifdef DEBUG_EXPR
+    char *dbg;
+#endif
+
+	/* the parser must be in the correct state */
+	if (!fypp || fy_expr_stack_size(&fypp->operators) > 0 || fy_expr_stack_size(&fypp->operands) > 0)
+		return NULL;
+
+	fyr = &fypp->reader;
+
+	/* find stream start */
+	fyt = fy_path_scan_peek(fypp, NULL);
+	FYR_PARSE_ERROR_CHECK(fyr, 0, 1, FYEM_PARSE,
+			fyt && fyt->type == FYTT_STREAM_START, err_out,
+			"no tokens available or start without stream start");
+
+	/* remove stream start */
+	fy_token_unref(fy_path_scan_remove(fypp, fyt));
+	fyt = NULL;
+
+	prev_scan_mode = fypp->expr_mode;
+
+	while ((fyt = fy_path_scan_peek(fypp, NULL)) != NULL) {
+
+		if (fyt->type == FYTT_STREAM_END)
+			break;
+
+#ifdef DEBUG_EXPR
+        fy_token_debug_text_a(fyt, &dbg);
+		FYR_TOKEN_DIAG(fyr, fyt, FYET_NOTICE, FYEM_PARSE, "next token %s", dbg);
+#endif
+		fytt = fyt->type;
+
+		/* create an expression in either operator/operand case */
+		expr = fy_path_expr_alloc_recycle(fypp);
+		fyr_error_check(fyr, expr, err_out,
+				"fy_path_expr_alloc_recycle() failed\n");
+
+		expr->fyt = fy_path_scan_remove(fypp, fyt);
+		/* this it the first attempt, it might not be the final one */
+		expr->type = fy_map_token_to_path_expr_type(fyt->type, fypp->expr_mode);
+		fyt = NULL;
+
+#ifdef DEBUG_EXPR
+		fy_path_expr_dump(expr, fypp->cfg.diag, FYET_NOTICE, 0, "-> expr");
+#endif
+
+		if (prev_scan_mode != fypp->expr_mode) {
+#ifdef DEBUG_EXPR
+			fyr_warning(fyr, "switched expr_mode %s -> %s\n",
+					fy_expr_mode_txt[prev_scan_mode],
+					fy_expr_mode_txt[fypp->expr_mode]);
+#endif
+			expr_top = fy_expr_stack_peek(&fypp->operators);
+
+#ifdef DEBUG_EXPR
+			if (expr_top)
+				fy_path_expr_dump(expr_top, fypp->cfg.diag, FYET_NOTICE, 0, NULL);
+#endif
+
+			if (expr_top && fy_path_expr_type_is_lparen(expr_top->type) &&
+					expr_top->expr_mode != fypp->expr_mode) {
+#ifdef DEBUG_EXPR
+				fyr_warning(fyr, "switched top lparen expr_mode %s -> %s\n",
+						fy_expr_mode_txt[expr_top->expr_mode],
+						fy_expr_mode_txt[fypp->expr_mode]);
+				expr_top->expr_mode = fypp->expr_mode;
+#endif
+			}
+		}
+
+		prev_scan_mode = fypp->expr_mode;
+
+		/* if it's an operand convert it to expression and push */
+		if (fy_token_type_is_operand(fytt)) {
+
+			ret = fy_expr_stack_push(&fypp->operands, expr);
+			fyr_error_check(fyr, !ret, err_out, "push_operand() failed\n");
+			expr = NULL;
+
+			continue;
+		}
+
+		/* specials for SLASH */
+
+		if (expr->fyt->type == FYTT_PE_SLASH) {
+
+			/* try to get next token */
+			fyt = fy_path_scan_peek(fypp, NULL);
+			if (!fyt) {
+				if (!fypp->stream_error) {
+					(void)fy_path_fetch_tokens(fypp);
+					fyt = fy_path_scan_peek(fypp, NULL);
+				}
+			}
+
+			/* last token, it means it's a collection filter (or a root) */
+			if (!fyt || fyt->type == FYTT_STREAM_END || fyt->type == FYTT_PE_RPAREN) {
+
+				exprt = fy_expr_stack_peek(&fypp->operands);
+
+				/* if no argument exists it's a root */
+				if (!exprt) {
+					expr->type = fpet_root;
+
+					ret = fy_expr_stack_push(&fypp->operands, expr);
+					fyr_error_check(fyr, !ret, err_out, "push_operand() failed\n");
+					expr = NULL;
+					continue;
+				}
+
+				expr->type = fpet_filter_collection;
+			}
+		}
+
+#ifdef DEBUG_EXPR
+		fy_notice(fypp->cfg.diag, "operator stack (before)\n");
+		fy_expr_stack_dump(fypp->cfg.diag, &fypp->operators);
+		fy_notice(fypp->cfg.diag, "operand stack (before)\n");
+		fy_expr_stack_dump(fypp->cfg.diag, &fypp->operands);
+#endif
+
+		old_scan_mode = fypp->expr_mode;
+
+		/* for rparen, need to push before */
+		if (expr->type == fpet_rparen) {
+
+			FYR_TOKEN_ERROR_CHECK(fyr, expr->fyt, FYEM_PARSE,
+					fypp->paren_nest_level > 0, err_out,
+					"Mismatched right parentheses");
+
+			fypp->paren_nest_level--;
+
+			ret = fy_expr_stack_push(&fypp->operators, expr);
+			fyr_error_check(fyr, !ret, err_out, "push_operator() failed\n");
+			expr = NULL;
+
+			ret = evaluate_new(fypp);
+			/* evaluate will print diagnostic on error */
+			if (ret < 0)
+				goto err_out;
+
+		} else if (fy_path_expr_type_is_lparen(expr->type)) {
+
+			expr->expr_mode = fypp->expr_mode;
+			fypp->expr_mode = fyem_scalar;
+
+			fypp->paren_nest_level++;
+
+			/* push the operator */
+			ret = fy_expr_stack_push(&fypp->operators, expr);
+			fyr_error_check(fyr, !ret, err_out, "push_operator() failed\n");
+			expr = NULL;
+
+#ifdef DEBUG_EXPR
+			if (old_scan_mode != fypp->expr_mode)
+				fyr_notice(fyr, "expr_mode %s -> %s\n",
+						fy_expr_mode_txt[old_scan_mode],
+						fy_expr_mode_txt[fypp->expr_mode]);
+#endif
+		} else {
+			switch (fypp->expr_mode) {
+			case fyem_none:
+				assert(0);	/* should never happen */
+				break;
+
+			case fyem_path:
+				if (fy_path_expr_type_is_conditional(expr->type)) {
+					/* switch to scalar mode */
+					fypp->expr_mode = fyem_scalar;
+					break;
+				}
+				break;
+			case fyem_scalar:
+				if (expr->type == fpet_root) {
+					fypp->expr_mode = fyem_path;
+					break;
+				}
+
+				/* div out of parentheses, it's a chain */
+				if (expr->type == fpet_div && fypp->paren_nest_level == 0) {
+					expr->type = fpet_chain;
+					fypp->expr_mode = fyem_path;
+
+					/* mode change means evaluate */
+					ret = evaluate_new(fypp);
+					/* evaluate will print diagnostic on error */
+					if (ret < 0)
+						goto err_out;
+
+					break;
+				}
+				break;
+			}
+
+			if (old_scan_mode != fypp->expr_mode) {
+#ifdef DEBUG_EXPR
+				fyr_notice(fyr, "expr_mode %s -> %s\n",
+						fy_expr_mode_txt[old_scan_mode],
+						fy_expr_mode_txt[fypp->expr_mode]);
+#endif
+			}
+
+			ret = -1;
+			while ((expr_top = fy_expr_stack_peek(&fypp->operators)) != NULL &&
+				fy_path_expr_type_prec(expr->type) <= fy_path_expr_type_prec(expr_top->type) &&
+				!fy_path_expr_type_is_lparen(expr_top->type)) {
+
+				ret = evaluate_new(fypp);
+				/* evaluate will print diagnostic on error */
+				if (ret < 0)
+					goto err_out;
+			}
+
+			/* push the operator */
+			ret = fy_expr_stack_push(&fypp->operators, expr);
+			fyr_error_check(fyr, !ret, err_out, "push_operator() failed\n");
+			expr = NULL;
+		}
+
+#ifdef DEBUG_EXPR
+		fy_notice(fypp->cfg.diag, "operator stack (after)\n");
+		fy_expr_stack_dump(fypp->cfg.diag, &fypp->operators);
+		fy_notice(fypp->cfg.diag, "operand stack (after)\n");
+		fy_expr_stack_dump(fypp->cfg.diag, &fypp->operands);
+#endif
+
+		prev_scan_mode = fypp->expr_mode;
+	}
+
+	if (fypp->stream_error)
+		goto err_out;
+
+	FYR_PARSE_ERROR_CHECK(fyr, 0, 1, FYEM_PARSE,
+			fypp->stream_error || (fyt && fyt->type == FYTT_STREAM_END), err_out,
+			"stream ended without STREAM_END");
+
+	/* remove stream end */
+	fy_token_unref(fy_path_scan_remove(fypp, fyt));
+	fyt = NULL;
+
+#if 0
+	FYR_PARSE_ERROR_CHECK(fyr, 0, 1, FYEM_PARSE,
+			fypp->paren_nest_level == 0, err_out,
+			"Missing right parenthesis");
+#endif
+
+	/* drain */
+	while ((expr_top = fy_expr_stack_peek(&fypp->operators)) != NULL &&
+		!fy_path_expr_type_is_lparen(expr_top->type)) {
+
+		ret = evaluate_new(fypp);
+		/* evaluate will print diagnostic on error */
+		if (ret < 0)
+			goto err_out;
+
+	}
+
+#ifdef DEBUG_EXPR
+	expr_top = fy_expr_stack_peek(&fypp->operators);
+	if (expr_top)
+		fy_path_expr_dump(expr_top, fypp->cfg.diag, FYET_NOTICE, 0, "operator top left");
+#endif
+
+	expr = fy_expr_stack_pop(&fypp->operands);
+
+	FYR_PARSE_ERROR_CHECK(fyr, 0, 1, FYEM_PARSE,
+			expr != NULL, err_out,
+			"No operands left on operand stack");
+
+	FYR_TOKEN_ERROR_CHECK(fyr, expr->fyt, FYEM_PARSE,
+			fy_expr_stack_size(&fypp->operands) == 0, err_out,
+			"Operand stack contains more than 1 value at end");
+
+	/* check the expression for validity */
+	rc = fy_path_check_expression(fypp, expr);
+	if (rc) {
+		fy_path_expr_free(expr);
+		expr = NULL;
+	}
+
+	return expr;
+
+err_out:
+#ifdef DEBUG_EXPR
+	fy_notice(fypp->cfg.diag, "operator stack (error)\n");
+	fy_expr_stack_dump(fypp->cfg.diag, &fypp->operators);
+	fy_notice(fypp->cfg.diag, "operand stack (error)\n");
+	fy_expr_stack_dump(fypp->cfg.diag, &fypp->operands);
+#endif
+	fypp->stream_error = true;
+	return NULL;
+}
+
+static struct fy_node *
+fy_path_expr_execute_single_result(struct fy_diag *diag, struct fy_path_expr *expr, struct fy_node *fyn)
+{
+	struct fy_token *fyt;
+	struct fy_anchor *fya;
+	const char *text;
+	size_t len;
+
+	assert(expr);
+
+	switch (expr->type) {
+	case fpet_root:
+		return fyn->fyd->root;
+
+	case fpet_this:
+		if (fy_node_is_alias(fyn)) {
+			// fprintf(stderr, "%s:%d %s calling fy_node_alias_resolve_by_ypath()\n", __func__, __LINE__, fy_node_get_path_alloca(fyn));
+			fyn = fy_node_alias_resolve_by_ypath(fyn);
+		}
+
+		return fyn;
+
+	case fpet_parent:
+		return fy_node_get_parent(fyn);
+
+	case fpet_alias:
+		fyt = expr->fyt;
+		assert(fyt);
+		assert(fyt->type == FYTT_PE_ALIAS);
+
+		text = fy_token_get_text(fyt, &len);
+		if (!text || len < 1)
+			break;
+
+		if (*text == '*') {
+			text++;
+			len--;
+		}
+		fya = fy_document_lookup_anchor(fyn->fyd, text, len);
+		if (!fya)
+			break;
+		return fya->fyn;
+
+	case fpet_seq_index:
+		fyt = expr->fyt;
+		assert(fyt);
+		assert(fyt->type == FYTT_PE_SEQ_INDEX);
+
+		if (fy_node_is_alias(fyn)) {
+			// fprintf(stderr, "%s:%d %s calling fy_node_alias_resolve_by_ypath()\n", __func__, __LINE__, fy_node_get_path_alloca(fyn));
+			fyn = fy_node_alias_resolve_by_ypath(fyn);
+		}
+
+		/* only on sequence */
+		if (!fy_node_is_sequence(fyn))
+			break;
+
+		return fy_node_sequence_get_by_index(fyn, fyt->seq_index.index);
+
+	case fpet_map_key:
+		fyt = expr->fyt;
+		assert(fyt);
+		assert(fyt->type == FYTT_PE_MAP_KEY);
+
+		if (fy_node_is_alias(fyn)) {
+			// fprintf(stderr, "%s:%d %s calling fy_node_alias_resolve_by_ypath()\n", __func__, __LINE__, fy_node_get_path_alloca(fyn));
+			fyn = fy_node_alias_resolve_by_ypath(fyn);
+		}
+
+		if (!fy_node_is_mapping(fyn))
+			break;
+
+		if (!fyt->map_key.fyd) {
+			/* simple key */
+			text = fy_token_get_text(fyt, &len);
+			if (!text || len < 1)
+				break;
+			return fy_node_mapping_lookup_value_by_simple_key(fyn, text, len);
+		}
+
+		return fy_node_mapping_lookup_value_by_key(fyn, fyt->map_key.fyd->root);
+
+	case fpet_filter_scalar:
+		if (!(fy_node_is_scalar(fyn) || fy_node_is_alias(fyn)))
+			break;
+		return fyn;
+
+	case fpet_filter_collection:
+
+		if (fy_node_is_alias(fyn)) {
+			// fprintf(stderr, "%s:%d %s calling fy_node_alias_resolve_by_ypath()\n", __func__, __LINE__, fy_node_get_path_alloca(fyn));
+			fyn = fy_node_alias_resolve_by_ypath(fyn);
+		}
+
+		if (!(fy_node_is_mapping(fyn) || fy_node_is_sequence(fyn)))
+			break;
+		return fyn;
+
+	case fpet_filter_sequence:
+
+		if (fy_node_is_alias(fyn)) {
+			// fprintf(stderr, "%s:%d %s calling fy_node_alias_resolve_by_ypath()\n", __func__, __LINE__, fy_node_get_path_alloca(fyn));
+			fyn = fy_node_alias_resolve_by_ypath(fyn);
+		}
+
+		if (!fy_node_is_sequence(fyn))
+			break;
+		return fyn;
+
+	case fpet_filter_mapping:
+
+		if (fy_node_is_alias(fyn)) {
+			// fprintf(stderr, "%s:%d %s calling fy_node_alias_resolve_by_ypath()\n", __func__, __LINE__, fy_node_get_path_alloca(fyn));
+			fyn = fy_node_alias_resolve_by_ypath(fyn);
+		}
+
+		if (!fy_node_is_mapping(fyn))
+			break;
+		return fyn;
+
+	default:
+		break;
+	}
+
+	return NULL;
+}
+
+static double
+token_number(struct fy_token *fyt)
+{
+	const char *value;
+
+	if (!fyt || fyt->type != FYTT_SCALAR || (value = fy_token_get_text0(fyt)) == NULL)
+		return NAN;
+	return strtod(value, NULL);
+}
+
+void fy_path_exec_cleanup(struct fy_path_exec *fypx)
+{
+	if (!fypx)
+		return;
+
+	fy_walk_result_free(fypx->result);
+	fypx->result = NULL;
+	fypx->fyn_start = NULL;
+}
+
+/* publicly exported methods */
+struct fy_path_parser *fy_path_parser_create(const struct fy_path_parse_cfg *pcfg)
+{
+	struct fy_path_parser *fypp;
+
+	fypp = malloc(sizeof(*fypp));
+	if (!fypp)
+		return NULL;
+	fy_path_parser_setup(fypp, pcfg);
+	return fypp;
+}
+
+void fy_path_parser_destroy(struct fy_path_parser *fypp)
+{
+	if (!fypp)
+		return;
+	fy_path_parser_cleanup(fypp);
+	free(fypp);
+}
+
+int fy_path_parser_reset(struct fy_path_parser *fypp)
+{
+	if (!fypp)
+		return -1;
+	fy_path_parser_cleanup(fypp);
+	return 0;
+}
+
+struct fy_path_expr *
+fy_path_parse_expr_from_string(struct fy_path_parser *fypp,
+			       const char *str, size_t len)
+{
+	struct fy_path_expr *expr = NULL;
+	struct fy_input *fyi = NULL;
+	int rc;
+
+	if (!fypp || !str || !len)
+		return NULL;
+
+	fy_path_parser_reset(fypp);
+
+	fyi = fy_input_from_data(str, len, NULL, false);
+	if (!fyi) {
+		fy_error(fypp->cfg.diag, "failed to create ypath input from %.*s\n",
+				(int)len, str);
+		goto err_out;
+	}
+
+	rc = fy_path_parser_open(fypp, fyi, NULL);
+	if (rc) {
+		fy_error(fypp->cfg.diag, "failed to open path parser input from %.*s\n",
+				(int)len, str);
+		goto err_out;
+	}
+
+	expr = fy_path_parse_expression(fypp);
+	if (!expr) {
+		fy_error(fypp->cfg.diag, "failed to parse path expression %.*s\n",
+				(int)len, str);
+		goto err_out;
+	}
+
+	fy_path_parser_close(fypp);
+
+	fy_input_unref(fyi);
+
+	return expr;
+
+err_out:
+	fy_path_expr_free(expr);
+	fy_path_parser_close(fypp);
+	fy_input_unref(fyi);
+	return NULL;
+}
+
+struct fy_path_expr *
+fy_path_expr_build_from_string(const struct fy_path_parse_cfg *pcfg,
+			       const char *str, size_t len)
+{
+	struct fy_path_parser fypp_data, *fypp = &fypp_data;
+	struct fy_path_expr *expr = NULL;
+
+	if (!str)
+		return NULL;
+
+	fy_path_parser_setup(fypp, pcfg);
+	expr = fy_path_parse_expr_from_string(fypp, str, len);
+	fy_path_parser_cleanup(fypp);
+
+	return expr;
+}
+
+struct fy_path_exec *fy_path_exec_create(const struct fy_path_exec_cfg *xcfg)
+{
+	struct fy_path_exec *fypx;
+
+	fypx = malloc(sizeof(*fypx));
+	if (!fypx)
+		return NULL;
+
+	memset(fypx, 0, sizeof(*fypx));
+	if (xcfg)
+		fypx->cfg = *xcfg;
+	fypx->fwr_recycle = NULL;	/* initially no recycling list */
+	fypx->refs = 1;
+
+	fypx->supress_recycling = !!(fypx->cfg.flags & FYPXCF_DISABLE_RECYCLING) ||
+		                  (getenv("FY_VALGRIND") &&
+				   !getenv("FY_VALGRIND_RECYCLING"));
+	return fypx;
+}
+
+struct fy_path_exec *fy_path_exec_create_on_document(struct fy_document *fyd)
+{
+	struct fy_path_exec_cfg xcfg_local, *xcfg = &xcfg_local;
+	struct fy_path_exec *fypx;
+
+	memset(xcfg, 0, sizeof(*xcfg));
+	xcfg->diag = fyd ? fyd->diag : NULL;
+
+	xcfg->flags = (fyd->parse_cfg.flags & FYPCF_DISABLE_RECYCLING) ?
+			FYPXCF_DISABLE_RECYCLING : 0;
+
+	fypx = fy_path_exec_create(xcfg);
+	if (!fypx)
+		return NULL;
+	return fypx;
+}
+
+void fy_path_exec_destroy(struct fy_path_exec *fypx)
+{
+	if (!fypx)
+		return;
+	fy_path_exec_cleanup(fypx);
+	free(fypx);
+}
+
+int fy_path_exec_reset(struct fy_path_exec *fypx)
+{
+	if (!fypx)
+		return -1;
+	fy_path_exec_cleanup(fypx);
+	return 0;
+}
+
+struct fy_walk_result *fy_walk_result_simplify(struct fy_walk_result *fwr)
+{
+	struct fy_walk_result *fwr2;
+#if 0
+	struct fy_walk_result *fwrf;
+	bool recursive;
+#endif
+
+	/* no fwr */
+	if (!fwr)
+		return NULL;
+
+	/* non recursive */
+	if (fwr->type != fwrt_refs)
+		return fwr;
+
+	/* refs, if empty, return NULL */
+	if (fy_walk_result_list_empty(&fwr->refs)) {
+		fy_walk_result_free(fwr);
+		return NULL;
+	}
+
+	/* single element, switch it out */
+	if (fy_walk_result_list_is_singular(&fwr->refs)) {
+		fwr2 = fy_walk_result_list_pop(&fwr->refs);
+		assert(fwr2);
+
+		fy_walk_result_free(fwr);
+		fwr = fwr2;
+	}
+
+	return fwr;
+#if 0
+	/* non recursive return immediately */
+	if (fwr->type != fwrt_refs)
+		return fwr;
+
+	/* flatten if recursive */
+	recursive = false;
+	for (fwr2 = fy_walk_result_list_head(&fwr->refs); fwr2;
+		fwr2 = fy_walk_result_next(&fwr->refs, fwr2)) {
+
+		/* refs, recursive */
+		if (fwr2->type == fwrt_refs) {
+			recursive = true;
+			break;
+		}
+	}
+
+	if (!recursive)
+		return fwr;
+
+	fwrf = fy_path_exec_walk_result_create(fypx, fwrt_refs);
+	assert(fwrf);
+
+	fy_walk_result_flatten_internal(fwr, fwrf);
+
+	fy_walk_result_free(fwr);
+	return fwrf;
+#endif
+
+}
+
+int fy_walk_result_all_children_recursive_internal(struct fy_path_exec *fypx, struct fy_node *fyn, struct fy_walk_result *output)
+{
+	struct fy_node *fyni;
+	struct fy_walk_result *fwr;
+	void *prevp;
+	int ret;
+
+	if (!fyn)
+		return 0;
+
+	assert(output);
+	assert(output->type == fwrt_refs);
+
+	/* this node */
+	fwr = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fyn);
+	if (!fwr)
+		return -1;
+	fy_walk_result_list_add_tail(&output->refs, fwr);
+
+	if (fy_node_is_scalar(fyn))
+		return 0;
+
+	prevp = NULL;
+	while ((fyni = fy_node_collection_iterate(fyn, &prevp)) != NULL) {
+		ret = fy_walk_result_all_children_recursive_internal(fypx, fyni, output);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+bool
+fy_walk_result_compare_simple(struct fy_path_exec *fypx, enum fy_path_expr_type type,
+			      struct fy_walk_result *fwrl, struct fy_walk_result *fwrr)
+{
+	struct fy_token *fyt;
+	struct fy_walk_result *fwrt;
+	const char *str;
+	bool match;
+
+	/* both NULL */
+	if (!fwrl && !fwrr) {
+		switch (type) {
+		case fpet_eq:
+			return true;
+		default:
+			break;
+		}
+		return false;
+	}
+
+	/* any NULL */
+	if (!fwrl || !fwrr) {
+		switch (type) {
+		case fpet_neq:
+			return true;
+		default:
+			break;
+		}
+		return false;
+	}
+
+	/* both are non NULL */
+
+	/* none should be multiple */
+	assert(fwrl->type != fwrt_refs && fwrr->type != fwrt_refs);
+
+	/* both are the same type */
+	if (fwrl->type == fwrr->type) {
+
+		switch (fwrl->type) {
+		case fwrt_none:
+			abort();	/* should never happen */
+			break;
+
+		case fwrt_node_ref:
+			switch (type) {
+			case fpet_eq:
+				/* simple and fast direct node comparison */
+				if (fwrl->fyn == fwrr->fyn)
+					return true;
+				return fy_node_compare(fwrl->fyn, fwrr->fyn);
+			case fpet_neq:
+				/* simple and fast direct node comparison */
+				if (fwrl->fyn != fwrr->fyn)
+					return true;
+				return !fy_node_compare(fwrl->fyn, fwrr->fyn);
+			default:
+				break;
+			}
+			break;
+
+		case fwrt_refs:
+			assert(0);	/* should not get here */
+			break;
+
+		case fwrt_doc:
+			switch (type) {
+			case fpet_eq:
+			case fpet_neq:
+				match = false;
+				if (fwrl->fyd == fwrr->fyd)
+					match = true;
+				else if (!fwrl->fyd || !fwrr->fyd)
+					match = false;
+				else
+					match = fy_node_compare(fwrl->fyd->root, fwrr->fyd->root);
+				if (type == fpet_neq)
+					match = !match;
+				return match;
+			default:
+				break;
+			}
+			break;
+
+		case fwrt_number:
+			switch (type) {
+			case fpet_eq:
+				return fwrl->number == fwrr->number;
+			case fpet_neq:
+				return fwrl->number != fwrr->number;
+			case fpet_lt:
+				return fwrl->number < fwrr->number;
+			case fpet_gt:
+				return fwrl->number > fwrr->number;
+			case fpet_lte:
+				return fwrl->number <= fwrr->number;
+			case fpet_gte:
+				return fwrl->number >= fwrr->number;
+			default:
+				break;
+			}
+			break;
+
+		case fwrt_string:
+			switch (type) {
+			case fpet_eq:
+				return strcmp(fwrl->string, fwrr->string) == 0;
+			case fpet_neq:
+				return strcmp(fwrl->string, fwrr->string) != 0;
+			case fpet_lt:
+				return strcmp(fwrl->string, fwrr->string) < 0;
+			case fpet_gt:
+				return strcmp(fwrl->string, fwrr->string) > 0;
+			case fpet_lte:
+				return strcmp(fwrl->string, fwrr->string) <= 0;
+			case fpet_gte:
+				return strcmp(fwrl->string, fwrr->string) >= 0;
+			default:
+				break;
+			}
+			break;
+		}
+		return false;
+	}
+
+	/* only handle the node refs at the left */
+	if (fwrr->type == fwrt_node_ref) {
+		switch (type) {
+		case fpet_lt:
+			type = fpet_gte;
+			break;
+		case fpet_gt:
+			type = fpet_lte;
+			break;
+		case fpet_lte:
+			type = fpet_gt;
+			break;
+		case fpet_gte:
+			type = fpet_lt;
+			break;
+		default:
+			break;
+		}
+
+		/* swap left with right */
+		return fy_walk_result_compare_simple(fypx, type, fwrr, fwrl);
+	}
+
+	switch (fwrl->type) {
+	case fwrt_node_ref:
+
+		/* non scalar mode, only returns true for non-eq */
+		if (!fy_node_is_scalar(fwrl->fyn)) {
+			/* XXX case of rhs being a document not handled */
+			return type == fpet_neq;
+		}
+
+		fyt = fy_node_get_scalar_token(fwrl->fyn);
+		assert(fyt);
+
+		str = fy_token_get_text0(fyt);
+		assert(str);
+
+		fwrt = NULL;
+		/* node ref against */
+		switch (fwrr->type) {
+		case fwrt_string:
+			/* create a new temporary walk result */
+			fwrt = fy_path_exec_walk_result_create(fypx, fwrt_string, str);
+			assert(fwrt);
+
+			break;
+
+		case fwrt_number:
+			/* if it's not a number return true only for non-eq */
+			if (!fy_token_is_number(fyt))
+				return type == fpet_neq;
+
+			/* create a new temporary walk result */
+			fwrt = fy_path_exec_walk_result_create(fypx, fwrt_number, strtod(str, NULL));
+			assert(fwrt);
+			break;
+
+		default:
+			break;
+		}
+
+		if (!fwrt)
+			return false;
+
+		match = fy_walk_result_compare_simple(fypx, type, fwrt, fwrr);
+
+		/* free the temporary result */
+		fy_walk_result_free(fwrt);
+
+		return match;
+
+	default:
+		break;
+	}
+
+	return false;
+}
+
+struct fy_walk_result *
+fy_walk_result_arithmetic_simple(struct fy_path_exec *fypx,
+				 struct fy_path_expr *expr,
+				 struct fy_path_expr *exprl, struct fy_walk_result *fwrl,
+				 struct fy_path_expr *exprr, struct fy_walk_result *fwrr)
+{
+	struct fy_diag *diag;
+	struct fy_walk_result *output = NULL;
+	char *str;
+	size_t len, len1, len2;
+
+	if (!fwrl || !fwrr)
+		goto out;
+
+	diag = fypx->cfg.diag;
+
+	/* node refs are not handled yet */
+	if (fwrl->type == fwrt_node_ref || fwrr->type == fwrt_node_ref)
+		goto out;
+
+	/* same type */
+	if (fwrl->type == fwrr->type) {
+
+		switch (fwrl->type) {
+
+		case fwrt_string:
+			/* for strings, only concatenation */
+			if (expr->type != fpet_plus)
+				break;
+			len1 = strlen(fwrl->string);
+			len2 = strlen(fwrr->string);
+			len = len1 + len2;
+			str = malloc(len + 1);
+			assert(str);
+			memcpy(str, fwrl->string, len1);
+			memcpy(str + len1, fwrr->string, len2);
+			str[len] = '\0';
+
+			free(fwrl->string);
+			fwrl->string = str;
+
+			/* reuse */
+			output = fwrl;
+			fwrl = NULL;
+
+			break;
+
+		case fwrt_number:
+			/* reuse fwrl */
+			output = fwrl;
+			switch (expr->type) {
+			case fpet_plus:
+				output->number = fwrl->number + fwrr->number;
+				break;
+			case fpet_minus:
+				output->number = fwrl->number - fwrr->number;
+				break;
+			case fpet_mult:
+				output->number = fwrl->number * fwrr->number;
+				break;
+			case fpet_div:
+				output->number = fwrr->number ? (fwrl->number / fwrr->number) : INFINITY;
+				break;
+			default:
+				assert(0);
+				break;
+			}
+			fwrl = NULL;
+			break;
+
+		default:
+			fy_error(diag, "fwrl->type=%s\n", fy_walk_result_type_txt[fwrl->type]);
+			assert(0);
+			break;
+		}
+	}
+
+out:
+	fy_walk_result_free(fwrl);
+	fy_walk_result_free(fwrr);
+	return output;
+}
+
+struct fy_walk_result *
+fy_walk_result_conditional_simple(struct fy_path_exec *fypx,
+				  struct fy_path_expr *expr,
+				  struct fy_path_expr *exprl, struct fy_walk_result *fwrl,
+				  struct fy_path_expr *exprr, struct fy_walk_result *fwrr)
+{
+	bool match;
+
+	match = fy_walk_result_compare_simple(fypx, expr->type, fwrl, fwrr);
+
+	if (!match) {
+		fy_walk_result_free(fwrl);
+		fy_walk_result_free(fwrr);
+		return NULL;
+	}
+
+	/* path expr, return left hand side result */
+	fy_walk_result_free(fwrr);
+	return fwrl;
+}
+
+struct fy_walk_result *
+fy_walk_result_lhs_rhs(struct fy_path_exec *fypx,
+		       struct fy_path_expr *expr,
+		       struct fy_path_expr *exprl, struct fy_walk_result *fwrl,
+		       struct fy_path_expr *exprr, struct fy_walk_result *fwrr)
+{
+	struct fy_walk_result *output = NULL, *fwr, *fwrrt, *fwrlt, *fwrlc, *fwrrc;
+	struct fy_walk_result *outputl = NULL, *outputr = NULL;
+
+	assert(expr);
+	assert(exprl);
+	assert(exprr);
+
+	/* only supports those */
+	if (!fy_path_expr_type_is_conditional(expr->type) &&
+	    !fy_path_expr_type_is_arithmetic(expr->type))
+		goto out;
+
+	/* both NULL */
+	if (!fwrl && !fwrr)
+		goto out;
+
+	/* any NULL */
+	if (!fwrl || !fwrr) {
+		if (expr->type == fpet_neq) {
+			output = fwrl;
+			fwrl = NULL;
+		}
+		goto out;
+	}
+
+	output = fy_path_exec_walk_result_create(fypx, fwrt_refs);
+	assert(output);
+
+	for (fwrlt = fy_walk_result_iter_start(fwrl); fwrlt;
+			fwrlt = fy_walk_result_iter_next(fwrl, fwrlt)) {
+
+		/* for recursive ones */
+		if (fwrlt->type == fwrt_refs) {
+
+			fwrlc = fy_walk_result_clone(fwrlt);
+			assert(fwrlc);
+			fwrrc = fy_walk_result_clone(fwrr);
+			assert(fwrrc);
+
+			outputl = fy_walk_result_lhs_rhs(fypx, expr, exprl, fwrlc, exprr, fwrrc);
+			if (outputl)
+				fy_walk_result_list_add_tail(&output->refs, outputl);
+			else
+				fy_walk_result_free(outputl);
+			continue;
+		}
+
+		/* non-recursive case */
+		for (fwrrt = fy_walk_result_iter_start(fwrr); fwrrt;
+				fwrrt = fy_walk_result_iter_next(fwrr, fwrrt)) {
+
+			/* for recursive ones */
+			if (fwrrt->type == fwrt_refs) {
+
+				fwrlc = fy_walk_result_clone(fwrlt);
+				assert(fwrlc);
+				fwrrc = fy_walk_result_clone(fwrrt);
+				assert(fwrrc);
+
+				outputr = fy_walk_result_lhs_rhs(fypx, expr, exprl, fwrlc, exprr, fwrrc);
+				if (outputr)
+					fy_walk_result_list_add_tail(&output->refs, outputr);
+				else
+					fy_walk_result_free(outputr);
+				continue;
+			}
+
+
+			fwrlc = fy_walk_result_clone(fwrlt);
+			assert(fwrlc);
+			fwrrc = fy_walk_result_clone(fwrrt);
+			assert(fwrrc);
+
+			fwr = NULL;
+
+			if (fy_path_expr_type_is_conditional(expr->type))
+				fwr = fy_walk_result_conditional_simple(fypx, expr, exprl, fwrlc, exprr, fwrrc);
+			else if (fy_path_expr_type_is_arithmetic(expr->type))
+				fwr = fy_walk_result_arithmetic_simple(fypx, expr, exprl, fwrlc, exprr, fwrrc);
+			else {
+				assert(0);
+			}
+
+			fwrlc = NULL;
+			fwrrc = NULL;
+
+			if (fwr)
+				fy_walk_result_list_add_tail(&output->refs, fwr);
+		}
+	}
+
+out:
+	fy_walk_result_free(fwrl);
+	fy_walk_result_free(fwrr);
+
+	return fy_walk_result_simplify(output);
+}
+
+struct fy_path_expr *
+fy_scalar_walk_result_to_expr(struct fy_path_exec *fypx, struct fy_walk_result *fwr, enum fy_path_expr_type ptype)
+{
+	struct fy_input *fyit = NULL;
+	struct fy_path_expr *exprt = NULL;
+	struct fy_atom handle;
+	bool collection_addressing;
+	char *buf;
+	int rc __FY_DEBUG_UNUSED__;
+
+	exprt = NULL;
+
+	if (!fwr)
+		return NULL;
+
+	collection_addressing = ptype == fpet_chain || ptype == fpet_multi;
+
+	switch (fwr->type) {
+	case fwrt_string:
+		fyit = fy_input_from_malloc_data(fwr->string, FY_NT, &handle, true);
+		assert(fyit);
+
+		fwr->string = NULL;
+		fy_walk_result_free(fwr);
+		fwr = NULL;
+
+		exprt = fy_path_expr_alloc();
+		assert(exprt);
+		if (collection_addressing) {
+			exprt->type = fpet_map_key;
+			exprt->fyt = fy_token_create(FYTT_PE_MAP_KEY, &handle, NULL);
+			assert(exprt->fyt);
+		} else {
+			exprt->type = fpet_scalar;
+			exprt->fyt = fy_token_create(FYTT_SCALAR, &handle, FYSS_PLAIN, NULL);
+			assert(exprt->fyt);
+		}
+		break;
+
+	case fwrt_number:
+
+		rc = asprintf(&buf, "%d", (int)fwr->number);
+		assert(rc != -1);
+
+		fyit = fy_input_from_malloc_data(buf, FY_NT, &handle, true);
+		assert(fyit);
+
+		exprt = fy_path_expr_alloc();
+		assert(exprt);
+		if (collection_addressing) {
+			exprt->type = fpet_seq_index;
+			exprt->fyt = fy_token_create(FYTT_PE_SEQ_INDEX, &handle, (int)fwr->number);
+			assert(exprt->fyt);
+		} else {
+			exprt->type = fpet_scalar;
+			exprt->fyt = fy_token_create(FYTT_SCALAR, &handle, FYSS_PLAIN, NULL);
+			assert(exprt->fyt);
+		}
+
+		break;
+
+	default:
+		break;
+	}
+
+	fy_walk_result_free(fwr);
+	fy_input_unref(fyit);
+
+	return exprt;
+}
+
+struct fy_walk_result *
+fy_path_expr_execute(struct fy_path_exec *fypx, int level, struct fy_path_expr *expr,
+		     struct fy_walk_result *input, enum fy_path_expr_type ptype)
+{
+	struct fy_diag *diag;
+	struct fy_walk_result *fwr, *fwrn, *fwrt, *fwrtn;
+	struct fy_walk_result *output = NULL, *input1, *output1, *input2, *output2;
+	struct fy_path_expr *exprn, *exprl, *exprr;
+	struct fy_node *fyn, *fynn, *fyni;
+	struct fy_token *fyt;
+	int start, end, count, i;
+	bool match;
+	struct fy_path_expr *exprt;
+	unsigned int nargs;
+	struct fy_walk_result **fwr_args;
+	void *prevp;
+	int rc __FY_DEBUG_UNUSED__;
+
+	/* error */
+	if (!fypx || !expr)
+		goto out;
+
+	diag = fypx->cfg.diag;
+
+#ifdef DEBUG_EXPR
+	if (input)
+		fy_walk_result_dump(input, diag, FYET_NOTICE, level, "input %s\n", fy_path_expr_type_txt[expr->type]);
+#endif
+
+	/* recursive */
+	if (input && input->type == fwrt_refs && !fy_path_expr_type_handles_refs(expr->type)) {
+
+		output = fy_path_exec_walk_result_create(fypx, fwrt_refs);
+		assert(output);
+
+		while ((fwr = fy_walk_result_list_pop(&input->refs)) != NULL) {
+
+			fwrn = fy_path_expr_execute(fypx, level + 1, expr, fwr, ptype);
+			if (fwrn)
+				fy_walk_result_list_add_tail(&output->refs, fwrn);
+		}
+		fy_walk_result_free(input);
+		input = NULL;
+		goto out;
+	}
+
+
+	/* single result case is common enough to optimize */
+	if (fy_path_expr_type_is_single_result(expr->type)) {
+
+		if (input && input->type == fwrt_node_ref) {
+
+			fynn = fy_path_expr_execute_single_result(diag, expr, input->fyn);
+			if (!fynn)
+				goto out;
+
+			fy_walk_result_clean(input);
+			output = input;
+			output->type = fwrt_node_ref;
+			output->fyn = fynn;
+			input = NULL;
+		}
+
+		goto out;
+	}
+
+	/* handle the remaining multi result cases */
+	switch (expr->type) {
+
+	case fpet_chain:
+
+		if (!input)
+			goto out;
+
+		/* iterate over each chain item */
+		output = input;
+		input = NULL;
+		for (exprn = fy_path_expr_list_head(&expr->children); exprn;
+			exprn = fy_path_expr_next(&expr->children, exprn)) {
+
+			output = fy_path_expr_execute(fypx, level + 1, exprn, output, expr->type);
+			if (!output)
+				break;
+		}
+
+		break;
+
+	case fpet_multi:
+
+		if (!input)
+			goto out;
+
+		/* allocate a refs output result */
+		output = fy_path_exec_walk_result_create(fypx, fwrt_refs);
+		assert(output);
+
+		/* iterate over each multi item */
+		for (exprn = fy_path_expr_list_head(&expr->children); exprn;
+			exprn = fy_path_expr_next(&expr->children, exprn)) {
+
+			input2 = fy_walk_result_clone(input);
+			assert(input2);
+
+			output2 = fy_path_expr_execute(fypx, level + 1, exprn, input2, expr->type);
+			if (!output2)
+				continue;
+
+			fy_walk_result_list_add_tail(&output->refs, output2);
+		}
+		fy_walk_result_free(input);
+		input = NULL;
+		break;
+
+	case fpet_every_child:
+
+		if (!input)
+			goto out;
+
+		/* only valid for node ref */
+		if (input->type != fwrt_node_ref)
+			break;
+
+		fyn = input->fyn;
+
+		/* every scalar/alias is a single result (although it should not happen) */
+		if (fy_node_is_scalar(fyn) || fy_node_is_alias(fyn)) {
+			output = input;
+			input = NULL;
+			break;
+
+		}
+
+		/* re-use input for output root */
+		fy_walk_result_clean(input);
+		output = input;
+		input = NULL;
+
+		output->type = fwrt_refs;
+		fy_walk_result_list_init(&output->refs);
+
+		prevp = NULL;
+		while ((fyni = fy_node_collection_iterate(fyn, &prevp)) != NULL) {
+			fwr = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fyni);
+			assert(fwr);
+
+			fy_walk_result_list_add_tail(&output->refs, fwr);
+		}
+
+		break;
+
+	case fpet_every_child_r:
+
+		if (!input)
+			goto out;
+
+		/* only valid for node ref */
+		if (input->type != fwrt_node_ref)
+			break;
+
+		fyn = input->fyn;
+
+		/* re-use input for output root */
+		fy_walk_result_clean(input);
+		output = input;
+		input = NULL;
+
+		output->type = fwrt_refs;
+		fy_walk_result_list_init(&output->refs);
+
+		rc = fy_walk_result_all_children_recursive_internal(fypx, fyn, output);
+		assert(!rc);
+
+		break;
+
+	case fpet_seq_slice:
+
+		if (!input)
+			goto out;
+
+		/* only valid for node ref on a sequence */
+		if (input->type != fwrt_node_ref || !fy_node_is_sequence(input->fyn)) {
+			break;
+		}
+		fyn = input->fyn;
+
+		fyt = expr->fyt;
+		assert(fyt);
+		assert(fyt->type == FYTT_PE_SEQ_SLICE);
+
+		start = fyt->seq_slice.start_index;
+		end = fyt->seq_slice.end_index;
+		count = fy_node_sequence_item_count(fyn);
+
+		/* don't handle negative slices yet */
+		if (start < 0 || end < 1 || start >= end)
+			break;
+
+		if (count < end)
+			end = count;
+
+		/* re-use input for output root */
+		fy_walk_result_clean(input);
+		output = input;
+		input = NULL;
+
+		output->type = fwrt_refs;
+		fy_walk_result_list_init(&output->refs);
+
+		for (i = start; i < end; i++) {
+
+			fynn = fy_node_sequence_get_by_index(fyn, i);
+			if (!fynn)
+				continue;
+
+			fwr = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fynn);
+			assert(fwr);
+
+			fy_walk_result_list_add_tail(&output->refs, fwr);
+		}
+
+		break;
+
+	case fpet_eq:
+	case fpet_neq:
+	case fpet_lt:
+	case fpet_gt:
+	case fpet_lte:
+	case fpet_gte:
+	case fpet_plus:
+	case fpet_minus:
+	case fpet_mult:
+	case fpet_div:
+
+		exprl = fy_path_expr_lhs(expr);
+		assert(exprl);
+
+		exprr = fy_path_expr_rhs(expr);
+		assert(exprr);
+
+		if (input) {
+			input1 = fy_walk_result_clone(input);
+			assert(input1);
+
+			input2 = input;
+			input = NULL;
+
+		} else {
+			input1 = NULL;
+			input2 = NULL;
+		}
+
+		/* execute LHS and RHS */
+		output1 = fy_path_expr_execute(fypx, level + 1, exprl, input1, expr->type);
+		output2 = fy_path_expr_execute(fypx, level + 1, exprr, input2, expr->type);
+
+		output = fy_walk_result_lhs_rhs(fypx, expr, exprl, output1, exprr, output2);
+
+		break;
+
+	case fpet_scalar:
+
+		/* duck typing! */
+		if (fy_token_is_number(expr->fyt)) {
+			output = fy_path_exec_walk_result_create(fypx, fwrt_number, token_number(expr->fyt));
+			assert(output);
+		} else {
+			output = fy_path_exec_walk_result_create(fypx, fwrt_string, fy_token_get_text0(expr->fyt));
+			assert(output);
+		}
+
+		fy_walk_result_free(input);
+		input = NULL;
+
+		break;
+
+	case fpet_logical_or:
+
+		/* return the first that is not NULL */
+		for (exprn = fy_path_expr_list_head(&expr->children); exprn;
+			exprn = fy_path_expr_next(&expr->children, exprn)) {
+
+			if (input) {
+				input1 = fy_walk_result_clone(input);
+				assert(input1);
+			} else {
+				input1 = NULL;
+			}
+
+			output = fy_path_expr_execute(fypx, level + 1, exprn, input1, expr->type);
+			if (output)
+				break;
+		}
+		break;
+
+	case fpet_logical_and:
+		output = NULL;
+
+		/* return the last that was not NULL */
+		for (exprn = fy_path_expr_list_head(&expr->children); exprn;
+			exprn = fy_path_expr_next(&expr->children, exprn)) {
+
+			if (input) {
+				input1 = fy_walk_result_clone(input);
+				assert(input1);
+			} else {
+				input1 = NULL;
+			}
+
+			output1 = fy_path_expr_execute(fypx, level + 1, exprn, input1, expr->type);
+			if (output1) {
+				fy_walk_result_free(output);
+				output = output1;
+			} else
+				break;
+		}
+		break;
+
+	case fpet_filter_unique:
+
+		if (!input)
+			goto out;
+
+		/* flatten input */
+		input = fy_walk_result_flatten(input);
+		assert(input);	/* must work */
+
+		/* for non refs, return input */
+		if (input->type != fwrt_refs) {
+			output = input;
+			input = NULL;
+			break;
+		}
+
+		/* remove duplicates filter */
+		for (fwr = fy_walk_result_list_head(&input->refs); fwr;
+				fwr = fy_walk_result_next(&input->refs, fwr)) {
+
+			/* do not check recursively */
+			if (fwr->type == fwrt_refs)
+				continue;
+
+			/* check the entries from this point forward */
+			for (fwrt = fy_walk_result_next(&input->refs, fwr); fwrt; fwrt = fwrtn) {
+
+				fwrtn = fy_walk_result_next(&input->refs, fwrt);
+
+				/* do not check recursively (or the same result) */
+				if (fwrt->type == fwrt_refs)
+					continue;
+
+				assert(fwrt != fwr);
+
+				match = fy_walk_result_compare_simple(fypx, fpet_eq, fwr, fwrt);
+
+				if (match) {
+					fy_walk_result_list_del(&input->refs, fwrt);
+					fy_walk_result_free(fwrt);
+				}
+			}
+		}
+		output = input;
+		input = NULL;
+
+		break;
+
+	case fpet_scalar_expr:
+
+		exprl = fy_path_expr_list_head(&expr->children);
+		if (!exprl) {
+			fy_warning(diag, "%s:%d\n", __FILE__, __LINE__);
+			goto out;
+		}
+
+		output = fy_path_expr_execute(fypx, level + 1, exprl, NULL, ptype);
+		if (!output) {
+			fy_warning(diag, "%s:%d\n", __FILE__, __LINE__);
+			goto out;
+		}
+
+		exprt = fy_scalar_walk_result_to_expr(fypx, output, ptype);
+		output = NULL;
+		if (!exprt) {
+			fy_warning(diag, "%s:%d\n", __FILE__, __LINE__);
+			break;
+		}
+
+		output = fy_path_expr_execute(fypx, level + 1, exprt, input, ptype);
+		if (!output) {
+			fy_warning(diag, "%s:%d\n", __FILE__, __LINE__);
+		}
+		input = NULL;
+
+		fy_path_expr_free(exprt);
+		break;
+
+	case fpet_path_expr:
+		exprl = fy_path_expr_list_head(&expr->children);
+		if (!exprl)
+			goto out;
+
+		output = fy_path_expr_execute(fypx, level + 1, exprl, input, ptype);
+		input = NULL;
+		break;
+
+	case fpet_method:
+
+		assert(expr->fym);
+
+		/* execute the arguments */
+		nargs = expr->fym->nargs;
+		if (nargs > 0) {
+			fwr_args = FY_ALLOCA(sizeof(*fwr_args) * nargs);
+			memset(fwr_args, 0, sizeof(*fwr_args) * nargs);
+			for (i = 0, exprt = fy_path_expr_list_head(&expr->children); exprt;
+					exprt = fy_path_expr_next(&expr->children, exprt), i++) {
+
+				if (input) {
+					input1 = fy_walk_result_clone(input);
+					assert(input1);
+				} else
+					input1 = NULL;
+
+				fwr_args[i] = fy_path_expr_execute(fypx, level + 1, exprt, input1, expr->type);
+			}
+		} else
+			fwr_args = NULL;
+
+		output = expr->fym->exec(expr->fym, fypx, level + 1, expr, input, fwr_args, nargs);
+		input = NULL;
+
+		break;
+
+	default:
+		fy_error(diag, "%s\n", fy_path_expr_type_txt[expr->type]);
+		assert(0);
+		break;
+	}
+
+out:
+	fy_walk_result_free(input);
+	output = fy_walk_result_simplify(output);
+
+#ifdef DEBUG_EXPR
+	if (output)
+		fy_walk_result_dump(output, diag, FYET_NOTICE, level, "output %s\n", fy_path_expr_type_txt[expr->type]);
+#endif
+	return output;
+}
+
+static int fy_path_exec_execute_internal(struct fy_path_exec *fypx,
+		struct fy_path_expr *expr, struct fy_node *fyn_start)
+{
+	struct fy_walk_result *fwr;
+
+	if (!fypx || !expr || !fyn_start)
+		return -1;
+
+	fy_walk_result_free(fypx->result);
+	fypx->result = NULL;
+
+	fwr = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fyn_start);
+	assert(fwr);
+
+	fwr = fy_path_expr_execute(fypx, 0, expr, fwr, fpet_none);
+	if (!fwr)
+		return 0;
+
+	/* flatten results */
+	if (fwr->type == fwrt_refs) {
+		fwr = fy_walk_result_flatten(fwr);
+		if (!fwr)
+			return -1;
+	}
+	fypx->result = fwr;
+
+	return 0;
+}
+
+int fy_path_exec_execute(struct fy_path_exec *fypx, struct fy_path_expr *expr, struct fy_node *fyn_start)
+{
+	if (!fypx || !expr || !fyn_start)
+		return -1;
+
+	fypx->fyn_start = fyn_start;
+	return fy_path_exec_execute_internal(fypx, expr, fypx->fyn_start);
+}
+
+struct fy_node *
+fy_path_exec_results_iterate(struct fy_path_exec *fypx, void **prevp)
+{
+	struct fy_walk_result *fwr;
+
+	if (!fypx || !prevp)
+		return NULL;
+
+	if (!fypx->result)
+		return NULL;
+
+	if (fypx->result->type != fwrt_refs) {
+		fwr = fypx->result;
+
+		if (fwr->type != fwrt_node_ref)
+			return NULL;
+
+		if (!*prevp) {
+			*prevp = fwr;
+			return fwr->fyn;
+		}
+		*prevp = NULL;
+		return NULL;
+	}
+
+	/* loop over non node refs for now */
+	do {
+		if (!*prevp)
+			fwr = fy_walk_result_list_head(&fypx->result->refs);
+		else
+			fwr = fy_walk_result_next(&fypx->result->refs, *prevp);
+		*prevp = fwr;
+	} while (fwr && fwr->type != fwrt_node_ref);
+
+	return fwr ? fwr->fyn : NULL;
+}
+
+struct fy_walk_result *
+fy_path_exec_take_results(struct fy_path_exec *fypx)
+{
+	struct fy_walk_result *fwr;
+
+	if (!fypx || !fypx->result)
+		return NULL;
+	fwr = fypx->result;
+	fypx->result = NULL;
+	return fwr;
+}
+
+struct fy_walk_result *
+fy_path_exec_walk_result_vcreate(struct fy_path_exec *fypx, enum fy_walk_result_type type, va_list ap)
+{
+	struct fy_walk_result_list *fwrl;
+
+	if (!fypx)
+		return NULL;
+
+	fwrl = fy_path_exec_walk_result_rl(fypx);
+	return fy_walk_result_vcreate_rl(fwrl, type, ap);
+}
+
+struct fy_walk_result *
+fy_path_exec_walk_result_create(struct fy_path_exec *fypx, enum fy_walk_result_type type, ...)
+{
+	struct fy_walk_result_list *fwrl;
+	struct fy_walk_result *fwr;
+	va_list ap;
+
+	if (!fypx)
+		return NULL;
+
+	fwrl = fy_path_exec_walk_result_rl(fypx);
+
+	va_start(ap, type);
+	fwr = fy_walk_result_vcreate_rl(fwrl, type, ap);
+	va_end(ap);
+
+	if (!fwr)
+		return NULL;
+
+	fwr->fypx = fy_path_exec_ref(fypx);
+
+	return fwr;
+}
+
+void
+fy_path_exec_walk_result_free(struct fy_path_exec *fypx, struct fy_walk_result *fwr)
+{
+	struct fy_walk_result_list *fwrl;
+
+	fwrl = fypx ? fy_path_exec_walk_result_rl(fypx) : NULL;
+	fy_walk_result_free_rl(fwrl, fwr);
+}
+
+int fy_document_setup_path_expr_data(struct fy_document *fyd)
+{
+	struct fy_path_parse_cfg pcfg_local, *pcfg = &pcfg_local;
+	struct fy_path_expr_document_data *pxdd;
+
+	if (!fyd || fyd->pxdd)
+		return 0;
+
+	pxdd = malloc(sizeof(*pxdd));
+	if (!pxdd)
+		goto err_no_mem;
+
+	memset(pxdd, 0, sizeof(*pxdd));
+
+	fy_walk_result_list_init(&pxdd->fwr_recycle);
+
+	memset(pcfg, 0, sizeof(*pcfg));
+	pcfg->diag = fyd->diag;
+	pxdd->fypp = fy_path_parser_create(pcfg);
+	if (!pxdd->fypp)
+		goto err_no_fypp;
+
+	fyd->pxdd = pxdd;
+
+	return 0;
+
+err_no_fypp:
+	free(pxdd);
+err_no_mem:
+	return -1;
+}
+
+void fy_document_cleanup_path_expr_data(struct fy_document *fyd)
+{
+	struct fy_path_expr_document_data *pxdd;
+	struct fy_walk_result *fwr;
+
+	if (!fyd || !fyd->pxdd)
+		return;
+
+	pxdd = fyd->pxdd;
+
+	fy_path_parser_destroy(pxdd->fypp);
+
+	while ((fwr = fy_walk_result_list_pop(&pxdd->fwr_recycle)) != NULL)
+		free(fwr);
+
+	free(fyd->pxdd);
+	fyd->pxdd = NULL;
+}
+
+int fy_node_setup_path_expr_data(struct fy_node *fyn)
+{
+	struct fy_path_expr_document_data *pxdd;
+	struct fy_path_expr_node_data *pxnd;
+	const char *text;
+	size_t len;
+	char *alloc = NULL;
+	int rc;
+
+	if (!fyn || fyn->pxnd)
+		return 0;
+
+	/* only on alias nodes */
+	if (!fy_node_is_alias(fyn))
+		return 0;
+
+	/* a document must exist */
+	if (!fyn->fyd)
+		return -1;
+
+	if (!fyn->fyd->pxdd) {
+		rc = fy_document_setup_path_expr_data(fyn->fyd);
+		if (rc)
+			return rc;
+	}
+	pxdd = fyn->fyd->pxdd;
+	assert(pxdd);
+
+	pxnd = malloc(sizeof(*pxnd));
+	if (!pxnd)
+		goto err_no_mem;
+	memset(pxnd, 0, sizeof(*pxnd));
+
+	text = fy_token_get_text(fyn->scalar, &len);
+	if (!text)
+		goto err_no_text;
+
+	if (!fy_is_first_alpha(*text)) {
+		pxnd->fyi = fy_input_from_data(text, len, NULL, false);
+		if (!pxnd->fyi)
+			goto err_no_input;
+	} else {
+		alloc = malloc(len + 2);
+		if (!alloc)
+			goto err_no_input;
+		alloc[0] = '*';
+		memcpy(alloc + 1, text, len);
+		alloc[len + 1] = '\0';
+
+		pxnd->fyi = fy_input_from_malloc_data(alloc, len + 1, NULL, false);
+		if (!pxnd->fyi)
+			goto err_no_input;
+	}
+
+	fy_path_parser_reset(pxdd->fypp);
+
+	rc = fy_path_parser_open(pxdd->fypp, pxnd->fyi, NULL);
+	if (rc)
+		goto err_no_open;
+
+	pxnd->expr = fy_path_parse_expression(pxdd->fypp);
+	if (!pxnd->expr)
+		goto err_parse;
+
+	fy_path_parser_close(pxdd->fypp);
+
+	fyn->pxnd = pxnd;
+
+	return 0;
+err_parse:
+	fy_path_parser_close(pxdd->fypp);
+err_no_open:
+	fy_input_unref(pxnd->fyi);
+err_no_input:
+	if (alloc)
+		free(alloc);
+err_no_text:
+	free(pxnd);
+err_no_mem:
+	return -1;
+}
+
+void fy_node_cleanup_path_expr_data(struct fy_node *fyn)
+{
+	struct fy_path_expr_node_data *pxnd;
+
+	if (!fyn || !fyn->pxnd)
+		return;
+
+	pxnd = fyn->pxnd;
+
+	if (pxnd->expr)
+		fy_path_expr_free(pxnd->expr);
+
+	if (pxnd->fyi)
+		fy_input_unref(pxnd->fyi);
+
+	free(pxnd);
+	fyn->pxnd = NULL;
+}
+
+struct fy_walk_result *
+fy_node_alias_resolve_by_ypath_result(struct fy_node *fyn)
+{
+	struct fy_document *fyd;
+	struct fy_path_expr_document_data *pxdd = NULL;
+	struct fy_path_expr_node_data *pxnd = NULL;
+	struct fy_walk_result *fwr;
+	struct fy_anchor *fya;
+	struct fy_path_exec *fypx = NULL;
+	int rc;
+	char* path;
+
+	if (!fyn || !fy_node_is_alias(fyn))
+		return NULL;
+
+	fyd = fyn->fyd;
+	if (!fyd)
+		return NULL;
+
+	/* simple */
+	fya = fy_document_lookup_anchor_by_token(fyd, fyn->scalar);
+	if (fya) {
+
+		fwr = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fya->fyn);
+		fyd_error_check(fyd, fwr, err_out,
+				"fy_walk_result_alloc_rl() failed");
+
+		return fwr;
+	}
+
+	/* ok, complex, setup the node data */
+	rc = fy_node_setup_path_expr_data(fyn);
+	fyd_error_check(fyd, !rc, err_out,
+			"fy_node_setup_path_expr_data() failed");
+
+	pxnd = fyn->pxnd;
+	assert(pxnd);
+
+	pxdd = fyd->pxdd;
+	assert(pxdd);
+
+	if (pxnd->traversals++ > 0) {
+        fy_node_get_path_alloca(fyn, &path);
+		FYD_NODE_ERROR(fyd, fyn, FYEM_DOC,
+				"recursive reference detected at %s\n",
+				path);
+		pxnd->traversals--;
+		return NULL;
+	}
+
+	fypx = fy_path_exec_create_on_document(fyd);
+	fyd_error_check(fyd, !rc, err_out,
+			"fy_path_exec_create_on_document() failed");
+
+	fy_path_exec_set_result_recycle_list(fypx, &pxdd->fwr_recycle);
+
+#if 0
+	{
+		struct fy_document *fyd_pe;
+		const char *text;
+		size_t len;
+
+		text = fy_token_get_text(fyn->scalar, &len);
+		if (text) {
+			fyd_pe = fy_path_expr_to_document(pxnd->expr);
+			if (fyd_pe) {
+				fprintf(stderr, "%s: %.*s\n", __func__, (int)len, text);
+				fy_document_default_emit_to_fp(fyd_pe, stderr);
+				fy_document_destroy(fyd_pe);
+			}
+		}
+	}
+#endif
+
+	// fprintf(stderr, "%s: %s 2\n", __func__, fy_node_get_path_alloca(fyn));
+
+	/* execute, starting at this */
+	rc = fy_path_exec_execute(fypx, pxnd->expr, fyn);
+	fyd_error_check(fyd, !rc, err_out,
+			"fy_path_exec_execute() failed");
+
+	// fprintf(stderr, "%s: %s 3\n", __func__, fy_node_get_path_alloca(fyn));
+
+	fwr = fy_path_exec_take_results(fypx);
+
+	fy_path_exec_unref(fypx);
+
+	pxnd->traversals--;
+
+	if (!fwr)
+		return NULL;
+
+	// fprintf(stderr, "%s: %s 4\n", __func__, fy_node_get_path_alloca(fyn));
+
+	return fwr;
+
+err_out:
+	if (pxnd)
+		pxnd->traversals--;
+	fy_path_exec_unref(fypx);	/* NULL OK */
+	return NULL;
+}
+
+struct fy_node *fy_node_alias_resolve_by_ypath(struct fy_node *fyn)
+{
+	struct fy_anchor *fya;
+	struct fy_walk_result *fwr;
+	void *iterp;
+
+	if (!fyn || !fy_node_is_alias(fyn))
+		return NULL;
+
+	/* simple and common enough to do it now */
+	fya = fy_document_lookup_anchor_by_token(fyn->fyd, fyn->scalar);
+	if (fya)
+		return fya->fyn;
+
+	fwr = fy_node_alias_resolve_by_ypath_result(fyn);
+	if (!fwr)
+		return NULL;
+
+	iterp = NULL;
+	fyn = fy_walk_result_node_iterate(fwr, &iterp);
+
+	fy_walk_result_free(fwr);
+
+	return fyn;
+}
+
+struct fy_walk_result *
+fy_node_by_ypath_result(struct fy_node *fyn, const char *path, size_t len)
+{
+	struct fy_path_expr_document_data *pxdd;
+	struct fy_document *fyd;
+	struct fy_walk_result *fwr;
+	struct fy_anchor *fya;
+	struct fy_input *fyi;
+	struct fy_path_expr *expr;
+	struct fy_path_exec *fypx = NULL;
+	int rc;
+
+	if (!fyn || !path || !len)
+		return NULL;
+
+	fyd = fyn->fyd;
+	if (!fyd)
+		return NULL;
+
+	if (len == FY_NT)
+		len = strlen(path);
+
+	/* simple */
+	fya = fy_document_lookup_anchor(fyn->fyd, path, len);
+	if (fya) {
+		fwr = fy_path_exec_walk_result_create(fypx, fwrt_node_ref, fya->fyn);
+		fyd_error_check(fyd, fwr, err_out,
+				"fy_walk_result_alloc_rl() failed");
+		return fwr;
+	}
+
+	/* ok, complex, setup the document data */
+	rc = fy_document_setup_path_expr_data(fyd);
+	fyd_error_check(fyd, !rc, err_setup,
+			"fy_node_setup_path_expr_data() failed");
+
+	pxdd = fyd->pxdd;
+	assert(pxdd);
+
+	fyi = fy_input_from_data(path, len, NULL, false);
+	fyd_error_check(fyd, fyi, err_no_input,
+			"fy_input_from_data() failed");
+
+	fy_path_parser_reset(pxdd->fypp);
+
+	rc = fy_path_parser_open(pxdd->fypp, fyi, NULL);
+	fyd_error_check(fyd, !rc, err_no_open,
+			"fy_path_parser_open() failed");
+
+	expr = fy_path_parse_expression(pxdd->fypp);
+	fyd_error_check(fyd, expr, err_parse,
+			"fy_path_parse_expression() failed");
+
+	fy_path_parser_close(pxdd->fypp);
+
+	fypx = fy_path_exec_create_on_document(fyd);
+	fyd_error_check(fyd, !rc, err_no_fypx,
+			"fy_path_exec_create_on_document() failed");
+
+	/* execute, starting at this */
+	rc = fy_path_exec_execute(fypx, expr, fyn);
+	fyd_error_check(fyd, !rc, err_exec,
+			"fy_path_parse_expression() failed");
+
+	fwr = fy_path_exec_take_results(fypx);
+
+	fy_path_exec_unref(fypx);
+
+	fy_path_expr_free(expr);
+	fy_input_unref(fyi);
+
+	return fwr;
+
+err_exec:
+	fy_path_expr_free(expr);
+err_no_fypx:
+	fy_path_exec_unref(fypx);
+err_parse:
+	fy_path_parser_close(pxdd->fypp);
+
+err_no_open:
+	fy_input_unref(fyi);
+
+err_no_input:
+err_setup:
+err_out:
+	return NULL;
+}
+
+struct fy_node *fy_node_by_ypath(struct fy_node *fyn, const char *path, size_t len)
+{
+	struct fy_walk_result *fwr;
+	struct fy_anchor *fya;
+	void *iterp;
+
+	if (!fyn || !path || !len)
+		return NULL;
+
+	/* simple */
+	fya = fy_document_lookup_anchor(fyn->fyd, path, len);
+	if (fya)
+		return fya->fyn;
+
+	fwr = fy_node_by_ypath_result(fyn, path, len);
+	if (!fwr)
+		return NULL;
+
+	iterp = NULL;
+	fyn = fy_walk_result_node_iterate(fwr, &iterp);
+
+	fy_walk_result_free(fwr);
+
+	return fyn;
+}