[Haskell-cafe] New OpenGL package: efficient way to convert datatypes?

The newest package seems to require using GLdouble/GLfloat. What is the most efficient way to convert Double/Float to GLdouble/GLfloat? I'm currently using realToFrac. But essentially the operation should be a nop on my machine. I haven't looked at the core code yet (on Windows, last time I checked, the ghc-core util did not work, and without it, reading core is even harder) Thanks, Peter