As I chunder on through OpenGL-land with Haskell I find things that sometimes confuse me! Is there some kind of assumption being made here about the remaining two zeros? color $ Color3 (0::GLfloat) 0 0 I can see that is is typing the first zero to GLfloat but why don't I need to do it to the remaining two zeros? Color3 is "Color3 !a !a !a" The !a is, IIUIC, a strictness instruction that ensures that whatever expression I put here is evaluated immediately i.e. no thunk is generated and presumably no space leaks either: something rendering at 60 fps with 'interesting' calculations for RGB values for example could cripple the application! But back to the syntax: I am guessing (and hoping I've got it right for the *right* reasons) that it works because the definition says "a" for all three and that explicitly typing the first one automatically tells (infers!) the type inference system that the other two are to be treated as GLfloat types too. :)