Yeah, I know, my doubt is more related to basic programming than anything else.
Now I did read the links you recommended properly, and I'm starting to understand a bit more about the problems related to floating comparisons (although it looks like I'm way too noob to get some of those stuff as of now). And a TimerFunc, in the case I need, looks a better option (than an IdleFunc).
Thanks for your reply, 'cause it opened my eyes to problems I didn't know existed. I'll just test and study more to get to the result I want.
The -1.5 was the initial X position of the object on the screen. Until that position was different then -2.3, the X variable should decrease -0.1, making it translate. Now I've created two global variables w/ the initial and final position, so I'm comparing these two.
Guys, thank you all for your answer. All your considerations were basically right, and now it is rotating perfectly. The main problem was that I wasn't applying glRotate when the object was first called and rendered.