From b58cfde48a1a175bf9e20940dccba70d2d581b42 Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Sun, 21 May 2023 15:13:57 +0200
Subject: [PATCH] BLI: improve IndexRange

Defining `operator-` for the iterator allows it to be used in more generic
iterator code. The `index_range` method is the same that exists on many
other containers like `Vector`.
---
 source/blender/blenlib/BLI_index_range.hh | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/source/blender/blenlib/BLI_index_range.hh b/source/blender/blenlib/BLI_index_range.hh
index 7f1266c6716..7991f68c5bc 100644
--- a/source/blender/blenlib/BLI_index_range.hh
+++ b/source/blender/blenlib/BLI_index_range.hh
@@ -105,6 +105,11 @@ class IndexRange {
       return a.current_ == b.current_;
     }
 
+    constexpr friend int64_t operator-(const Iterator &a, const Iterator &b)
+    {
+      return a.current_ - b.current_;
+    }
+
     constexpr int64_t operator*() const
     {
       return current_;
@@ -151,6 +156,11 @@ class IndexRange {
     return size_;
   }
 
+  constexpr IndexRange index_range() const
+  {
+    return IndexRange(size_);
+  }
+
   /**
    * Returns true if the size is zero.
    */