docs/features/core/data_structures/index_range.md

@@ -1 +1,21 @@
 # Index Range
+
+An `IndexRange` ([source](https://projects.blender.org/blender/blender/src/branch/main/source/blender/blenlib/BLI_index_range.hh)) represents a set of non-negative consecutive indices. It's stored as just the start index and the number of indices. Since it's small, it should generally be passed by value.
+
+The most common usage of `IndexRange` is to loop over indices. This is better than a c-style index loop, because it reduces the likelyhood of mixing up variables and allows the current index to be const. It's also just more convenient.
+
+```cpp
+/* Iterate over the indices from 0 to 9. */
+for (const int64_t i : IndexRange(10)) { /* ... */ }
+```
+
+Most container data structures have an `.index_range()` method which makes it easy to iterate over all the indices in the container.
+
+```cpp
+/* Iterate over indices in the container. */
+Vector<int> vec = /* ... */;
+for (const int64_t i : vec.index_range()) { /* ... */ }
+
+/* Iterate over the indices but skip the first 5. */
+for (const int64_t i : vec.index_range().drop_front(5)) { /* ... */ }
+```