C++20 constexpr math functions

In C++20, many math functions from the <cmath> library were made constexpr. This enables complex mathematical operations at compile time, which can lead to more efficient and optimized code.

The main advantage of using constexpr math functions is that they enable calculations at compile time rather than at runtime. This can lead to performance improvements because the compiler can optimize the code based on the known constant values. Additionally, because the values are known at compile time, they can be used in places where a constant expression is needed, such as in array sizes and template arguments.

Here are some important points to remember about constexpr math functions:

1. Only a subset of math functions from the <cmath> library are constexpr in C++20. Other functions may still be evaluated at runtime.

2. The arguments provided to a constexpr function must be constant expressions themselves. Otherwise, the function call will not be evaluated at compile time.

3. constexpr math functions are subject to the same floating-point rounding and accuracy limitations as their runtime counterparts. In other words, you should be aware of potential floating-point inaccuracies when using constexpr functions in calculations.

4. Some compilers may not yet fully support C++20 or all of its constexpr math functions. Be sure to check the documentation of the compiler being used to ensure that it supports the specific functions.

Here is a list of selected math functions that became constexpr in C++20. Note that this list is not exhaustive, but it covers some of the most commonly used functions. Once again, these functions became constexpr in C++20, not C++17.

Here's the table sorted by function name in ascending order: