diff --git a/stdlib/mem.jou b/stdlib/mem.jou
index f5a3f042..e7c3f6f5 100644
--- a/stdlib/mem.jou
+++ b/stdlib/mem.jou
@@ -24,3 +24,6 @@ declare memset(dest: void*, fill_byte: int, size: long) -> void*
 #   - it may be slightly faster.
 declare memcpy(dest: void*, source: void*, size: long) -> void*  # copy memory, overlaps are UB
 declare memmove(dest: void*, source: void*, size: long) -> void*  # copy memory, overlaps are ok
+
+# Swaps the contents of two memory regions of the same size.
+# This does nothing if the memory regions