record GLFunction[Names, Type] {
    ptr: Type;
}

[Names, Type]
pointerDereference(fn:GLFunction[Names, Type]) = ptr;

overloadable getGLProcAddress;

overload getGLProcAddress() {
    return null(Void);
}

overload getGLProcAddress(name:CString, ...) {
    var ptr = wglGetProcAddress(name);
    if (null?(ptr))
        return getGLProcAddress(...);
    else
        return ptr;
}

[Name, Type] initGLFunction(fn:GLFunction[Names,Type]) {
    fn.ptr <-- Type(getGLProcAddress(...Names));
}

// ... gl functions ...
var glDrawElements : GLFunction[
    ("glDrawElements", "glDrawElementsEXT", "glDrawElementsARB"),
    CCodePointer[GLenum, GLsizei, GLenum, Pointer[GLvoid], Void]
];
// ... gl functions ...

initAllGLFunctions() {
    // ... initGLFunction(gl function); ...
    initGLFunction(glDrawElements);
    // ... initGLFunction(gl function); ...
}

someGLFunction() {
    // ...
    glDrawElements^(GL_TRIANGLES, 100, GL_UNSIGNED_SHORT, vertices);
}