BLI: improve support for generic algorithms with c++ containers

Some generic algorithms from the standard library like `std::any_of`
did not work with all container and iterator types. To improve the
situation, this patch adds various type members to containers
and iterators.

Custom iterators for Set, Map and IndexRange now have an iterator
category, which soe algorithms require. IndexRange could become
a random access iterator, but adding all the missing methods can
be done when it is necessary.

1 files changed, 22 insertions, 3 deletions

diff --git a/source/blender/blenlib/BLI_index_range.hh b/source/blender/blenlib/BLI_index_range.hh
index 61a8088edea..665f44468db 100644
--- a/source/blender/blenlib/BLI_index_range.hh
+++ b/source/blender/blenlib/BLI_index_range.hh
@@ -82,11 +82,18 @@ class IndexRange {
   }
 
   class Iterator {
+   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = int64_t;
+    using pointer = const int64_t *;
+    using reference = const int64_t &;
+    using difference_type = std::ptrdiff_t;
+
    private:
     int64_t current_;
 
    public:
-    constexpr Iterator(int64_t current) : current_(current)
+    constexpr explicit Iterator(int64_t current) : current_(current)
     {
     }
 
@@ -96,9 +103,21 @@ class IndexRange {
       return *this;
     }
 
-    constexpr bool operator!=(const Iterator &iterator) const
+    constexpr Iterator operator++(int) const
+    {
+      Iterator copied_iterator = *this;
+      ++copied_iterator;
+      return copied_iterator;
+    }
+
+    constexpr friend bool operator!=(const Iterator &a, const Iterator &b)
+    {
+      return a.current_ != b.current_;
+    }
+
+    constexpr friend bool operator==(const Iterator &a, const Iterator &b)
     {
-      return current_ != iterator.current_;
+      return a.current_ == b.current_;
     }
 
     constexpr int64_t operator*() const