Adds move-only callable support to filter

Ryan Haining · Ryan Haining · commit 1c828d06d73d · 2025-02-10T13:11:58.000-08:00
Issue #89
diff --git a/cppitertools/filter.hpp b/cppitertools/filter.hpp
@@ -29,6 +29,8 @@ namespace iter {
 
 template <typename FilterFunc, typename Container>
 class iter::impl::Filtered {
+  static_assert(!std::is_reference_v<FilterFunc>);
+
  private:
   Container container_;
   mutable FilterFunc filter_func_;
@@ -39,7 +41,7 @@ class iter::impl::Filtered {
   // Value constructor for use only in the filter function
   Filtered(FilterFunc filter_func, Container&& container)
       : container_(std::forward<Container>(container)),
-        filter_func_(filter_func) {}
+        filter_func_(std::move(filter_func)) {}
 
  public:
   Filtered(Filtered&&) = default;
diff --git a/test/test_filter.cpp b/test/test_filter.cpp
@@ -25,6 +25,12 @@ TEST_CASE("filter: handles different callable types", "[filter]") {
     REQUIRE(v == vc);
   }
 
+  SECTION("with move-only callable object") {
+    auto f = filter(MoveOnlyLessThanValue{5}, ns);
+    Vec v(std::begin(f), std::end(f));
+    REQUIRE(v == vc);
+  }
+
   SECTION("with lambda") {
     auto ltf = [](int i) { return i < 5; };
     auto f = filter(ltf, ns);
