From cfec8308a39ae4a2a1a1b1fe0df0a099470d9c78 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 17 Oct 2024 02:58:16 +0100
Subject: Simple constexpr pow function

---
 lib/maths.cpp | 12 ++++++++++++
 lib/maths.h   | 13 +++++++++++++
 2 files changed, 25 insertions(+)

(limited to 'lib')

diff --git a/lib/maths.cpp b/lib/maths.cpp
index ea245f0..f527881 100644
--- a/lib/maths.cpp
+++ b/lib/maths.cpp
@@ -116,6 +116,18 @@ normalize(float ang)
 	return ang;
 }
 
+static_assert(pow(1, 0) == 1);
+static_assert(pow(1, 1) == 1);
+static_assert(pow(1, 2) == 1);
+static_assert(pow(2, 0) == 1);
+static_assert(pow(2, 1) == 2);
+static_assert(pow(2, 2) == 4);
+static_assert(pow(2, 3) == 8);
+static_assert(pow(3, 0) == 1);
+static_assert(pow(3, 1) == 3);
+static_assert(pow(3, 2) == 9);
+static_assert(pow(pi, 3) == 31.006278991699219F);
+
 float
 operator"" _mph(const long double v)
 {
diff --git a/lib/maths.h b/lib/maths.h
index 32f2884..97b7ef5 100644
--- a/lib/maths.h
+++ b/lib/maths.h
@@ -261,6 +261,19 @@ midpoint(const std::pair<T, T> & v)
 	return std::midpoint(v.first, v.second);
 }
 
+// std::pow is not constexpr
+template<typename T>
+	requires requires(T n) { n *= n; }
+constexpr inline T
+pow(const T base, std::integral auto exp)
+{
+	T res {1};
+	while (exp--) {
+		res *= base;
+	}
+	return res;
+}
+
 // Conversions
 template<typename T>
 inline constexpr auto
-- 
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