AK: Introduce IntegralMath.h starting with pow<I>

AK/IntegralMath.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2022, Leon Albrecht <leon2002.la@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Concepts.h>
+#include <AK/Types.h>
+
+#include <AK/Format.h>
+
+namespace AK {
+
+template<Integral I>
+constexpr I pow(I base, I exponent)
+{
+    // https://en.wikipedia.org/wiki/Exponentiation_by_squaring
+    if (exponent < 0)
+        return 0;
+    if (exponent == 0)
+        return 1;
+
+    I res = 1;
+    while (exponent > 0) {
+        if (exponent & 1)
+            res *= base;
+        base *= base;
+        exponent /= 2u;
+    }
+    return res;
+}
+
+}