GLUT: glutKeyboardFunc + glutSpecialFunc

Is it save to use one integer variable to hold both the values glutKeyboardFunc and glutSpecialFunc? Or do some numbers of glutSpecialFunc overlap with the ASCII values of glutKeyboardFunc?
Thanks in advance,

Special key codes overlap with ascii character codes. For example GLUT_KEY_LEFT has the same code as the character ‘d’.

Ok, thank you for your reply.

Ok, I have a problem with the functions glutKeyboardUpFunc & glutSpecialUpFunc.
I’m trying to get rid of the huge delay between the first charachter and the second character.
I do this by keeping track of the status of a button -> the key is still pressed until a release event is triggerd.
But my problem is that, when I register the callbacks for glutKeyboardUpFunc and glutSpecialUpFunc, the callbacks registered by glutSpecialFunc and glutKeyboardFunc are no longer called.
And to make it even worse, glutKeyboardUpFunc and glutSpecialUpFunc are called whenever the key is down, but when the key is released.
Is this a bug of GLUT, or is this a missunderstanding(about what these functions supposed todo) by me?
If it’s the latter, can you please help me do what I want.
Thanks in advance,