[libcxx-commits] [libcxx] [libcxx] adds ranges::fold_left_with_iter and ranges::fold_left (PR #75259)

[via libcxx-commits]

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@@ -87,4 +89,15 @@ void test() {
   std::ranges::unique(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   std::ranges::upper_bound(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   std::ranges::upper_bound(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+#if TEST_STD_VER >= 23
+  std::ranges::fold_left(range, 0, std::plus());
+  // expected-warning at -1{{ignoring return value of function declared with 'nodiscard' attribute}}
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EricWF wrote:

Sure. the binary operator can contain state. That state can be consumed after the algorithm has run. Consider an addition operator that checked for overflows and reported that out-of-band. 

It may not be good code, but it's correct code. 

https://github.com/llvm/llvm-project/pull/75259