Mathias Agopian 58b7084c8b make libmath much more constexpr friendly ...

It turns out that most of libmath couldn't be used in constexpr
expression due to our use of union{}. The C++ standard requires that
all accesses to a union{} in a constexpr expression be the same
element.

Also because libm and cmath are not constexpr some functions such
as length() or normalize() can't be constexpr. The same is true for
anything needing things like sqrt, cos, sin, ceil, floor.

This change mainly does the following:
- replace all accesses to vector elements by operator[]
  (this ensure all of libmath uses the same union element)

- avoid use of std::min / std::max / std::abs

- avoid uninitialized variables, which can't be constexpr

- remove 'constexpr' keyword on functions that can never be

It is now possible to write things like:

    constexpr mat4f I = inverse(
            transpose(mat4f::translation(float3{ 1, 2, 3 }) 
                 * mat4f::scaling(4)));

2019-07-18 16:48:37 -07:00

7.6 KiB

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