util: simpler implementation of the `EqualToOneOf` and `CountOf` algorithms using the fold expression

62d55507536a408dd9c37a5497efaa0a1333cc6c

1 files changed, 6 insertions, 16 deletions

diff --git a/util/generic/algorithm.h b/util/generic/algorithm.h
index bf32a19643..8286275e79 100644
--- a/util/generic/algorithm.h
+++ b/util/generic/algorithm.h
@@ -208,24 +208,14 @@ constexpr size_t FindIndexIf(C&& c, P p) {
 }
 
 //EqualToOneOf(x, "apple", "orange") means (x == "apple" || x == "orange")
-template <typename T>
-constexpr bool EqualToOneOf(const T&) {
-    return false;
+template <typename T, typename... Other>
+constexpr bool EqualToOneOf(const T& x, const Other&... values) {
+    return (... || (x == values));
 }
 
-template <typename T, typename U, typename... Other>
-constexpr bool EqualToOneOf(const T& x, const U& y, const Other&... other) {
-    return x == y || EqualToOneOf(x, other...);
-}
-
-template <typename T>
-constexpr size_t CountOf(const T&) {
-    return 0;
-}
-
-template <typename T, typename U, typename... Other>
-constexpr size_t CountOf(const T& x, const U& y, const Other&... other) {
-    return static_cast<size_t>(x == y) + CountOf(x, other...);
+template <typename T, typename... Other>
+constexpr size_t CountOf(const T& x, const Other&... values) {
+    return (0 + ... + static_cast<size_t>(x == values));
 }
 
 template <class I>