g-truc/glm — pull request #275 by plasmacel (2014-11-24 01:11:06+00:00)
Title: add explicit matrix conversion operators to quat

as you stated in issue #274, adding explicit constructors (for quat) to matrix types would break the spirit of the library. however this feature can be achieved by adding explicit conversion operators to glm::quat. this way the core profile remains unpolluted, according to the GLSL standard. so the feature only available if GTC_quaternion extension is used.