From f879e041339ee414ddb9514a0883baa66ce34f6d Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Thu, 22 Jul 2021 19:07:17 +0430
Subject: [PATCH] AK: Add a concept for iterable containers

This concept describes a type with a begin()/end() pair that can
function as an iterator, given the following criteria:
- The return type of begin() is comparable with the return type of
  end(), and the comparison (with operator!=) yields a bool
- The object returned from begin() can be pre-incremented
- The iterator has an operator*() implementation
---
 AK/Concepts.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/AK/Concepts.h b/AK/Concepts.h
index ced4b291424..697a8f1ec0b 100644
--- a/AK/Concepts.h
+++ b/AK/Concepts.h
@@ -51,6 +51,21 @@ concept IteratorFunction = requires(Func func, Args... args)
     }
     -> SameAs<IterationDecision>;
 };
+
+template<typename T, typename EndT>
+concept IteratorPairWith = requires(T it, EndT end)
+{
+    *it;
+    { it != end } -> SameAs<bool>;
+    ++it;
+};
+
+template<typename T>
+concept IterableContainer = requires
+{
+    { declval<T>().begin() } -> IteratorPairWith<decltype(declval<T>().end())>;
+};
+
 // clang-format on
 }
 
@@ -58,7 +73,9 @@ using AK::Concepts::Arithmetic;
 using AK::Concepts::Enum;
 using AK::Concepts::FloatingPoint;
 using AK::Concepts::Integral;
+using AK::Concepts::IterableContainer;
 using AK::Concepts::IteratorFunction;
+using AK::Concepts::IteratorPairWith;
 using AK::Concepts::Signed;
 using AK::Concepts::Unsigned;
 using AK::Concepts::VoidFunction;