glm::to_string on quaternions writes components in the wrong order

[zoopp]

I was debugging an issue in my code and I had to visually inspect the value of a quaternion so I turned to glm::to_string to provide me with a textual representation. Without even thinking about it, I was expecting the output to be in {w, x, y, z} order because that's how I've seen it presented in online resources that I've been learning from. Unfortunately, that was not the case as the order in which the output is written is {x, y, z, w}.

This hasn't affected me much but I did lose some time because of it and I don't think this is intended behaviour.

Sample code to reproduce the issue:

#include <iostream>

#include <glm/gtc/quaternion.hpp>
#include <glm/gtx/string_cast.hpp>

int main() {
    auto a = glm::quat{1.0f, {2.0f, 3.0f, 4.0f}};
    std::cout << "Version: " << GLM_VERSION << '\n'
              << glm::to_string(a) << "\n"
              << "a{w, x, y, z} = "
              << "{" << a.w << ", " << a.x << ", " << a.y << ", " << a.z << "}\n";
    return 0;
}

Sample output:

Version: 98
quat(2.000000, 3.000000, 4.000000, 1.000000)
a{w, x, y, z} = {1, 2, 3, 4}

I've looked around in the code and I see that this is a trivial fix. I can submit a pull request if this should be addressed.

[Groovounet]

This issue is fixed in master branch for GLM 0.9.9 release.

Thanks for contributing,
Christophe