From bbb256e8b50e38dd8b68f39827de5bad8c1d4a6e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?kleines=20Filmr=C3=B6llchen?= <filmroellchen@serenityos.org>
Date: Thu, 21 Apr 2022 10:41:27 +0200
Subject: [PATCH] AK: Introduce Indexable concept

This was dearly missing and can be used in many existing templates.
---
 AK/Concepts.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/AK/Concepts.h b/AK/Concepts.h
index 8b193d5127..6368310bfa 100644
--- a/AK/Concepts.h
+++ b/AK/Concepts.h
@@ -79,6 +79,16 @@ concept ArrayLike = requires(ArrayT array, SizeT index)
     -> SameAs<RemoveReference<ContainedT>*>;
 };
 
+// Any indexable data structure.
+template<typename ArrayT, typename ContainedT, typename SizeT = size_t>
+concept Indexable = requires(ArrayT array, SizeT index)
+{
+    {
+        array[index]
+    }
+    -> OneOf<RemoveReference<ContainedT>&, RemoveReference<ContainedT>>;
+};
+
 template<typename Func, typename... Args>
 concept VoidFunction = requires(Func func, Args... args)
 {
@@ -130,6 +140,7 @@ using AK::Concepts::Enum;
 using AK::Concepts::FallibleFunction;
 using AK::Concepts::FloatingPoint;
 using AK::Concepts::Fundamental;
+using AK::Concepts::Indexable;
 using AK::Concepts::Integral;
 using AK::Concepts::IterableContainer;
 using AK::Concepts::IteratorFunction;