cste_math

constexpr scalar math.

#include "cste_math/cste_math.h"

namespace cm = cste_math;

constexpr float val = cm::sine(cm::pi<float> / 3.0f);
constexpr double val_2 = cm::square_root(3.0);

Quick Start

Prerequisites

All you need is a compiler that implements c++20's std::is_is_constant_evaluated.

Installation

include

cste_math is a header-only library. As such, all you need to do is make the contents of the include directory available to your compiler.

CMake

While the cmake project is primarily used to manage tests and deployment, it's still set up as a proper target-exporting project. So you can use either add_subdirectory(path/to/cste_math_source) or find_package(cste_math) and use target_link_libraries(my_target cste_math::cste_math).

Usage

#include "cste_math/cste_math.h"

void foo() {
	constexpr float sq_2 = cste::square_root(2.0f);
}

Compile-time vs runtime

When you use functions defined in the root cste namespace, the library will choose wether to use a constexpr or an efficient runtime implementation based on context. This is important because some constexpr implementations are substantially slower than their runtime equivalent.

At first glance, that doesn't sound liek a major issue. However, because of this, the library cannot guarantee that the result will always be the same.

If you find yourself in a situation where you need that guarantee for whatever reason, you can force the use of the compile-time algorithm by using the cste::ct namespace, at the cost of some performance.

#include "cste_math/cste_math.h"

void foo() {
  constexpr float v_a = cste::exponential(0.1234f);
  float v_b = cste::exponential(0.1234f);

  assert(v_a == v_b); // WATCH OUT! Not necessarily the case!
}

void bar() {
  constexpr float v_a = cste::exponential(0.1234f);
  float v_b = cste::ct::exponential(0.1234f);

  assert(v_a == v_b); // Guaranteed.
}

Quick Reference

Constants

How	What
e<T>	e
pi<T>	π
two_pi<T>	2π
half_pi<T>	π/2
quarter_pi<T>	π/4
two_pi<T>	2π

Calculus

How	What
T absolute(const T& x);	|x|
T exponential(const T& x);	ex
T modulo(const T& x, const T& y);	remainder of x/y
T power(const T& x, const T& y);	xy
T square_root(const T& x);	√x

Number identification

How	What
bool is_inf(const T& x);	Checks for infinity
bool is_nan(const T& x);	Checks for nan
T sign(const T& x);	negative: -1, positive: 1, zero: 0

Rounding

How	What
T round_up(const T& x);	round number up
T round_down(const T& x);	round number down
T round(const T& x);	round number to closest integer
T truncate(const T& x);	round number towards 0
T fractional(const T& x);	The fractional part of the number

Trigonometry functions

How	What
T sine(const T& rad);	sin(rad)
T cosine(const T& rad);	cos(rad)
T tangent(const T& rad);	tan(rad)

Preemptive FAQs

f(x) is not in the library!

File a bug! Or even better, add it yourself and send us a pull request. The library is currently being developped on a as-needed basis.

Why are functions not named consistently with established conventions?

cste_math is not guaranteed to return values that are going to 100% match their standard library equivalent on all platforms. Having different functions names helps in preventing people from assuming that could be the case.