Also, btw, you have an error in your logic of 0 are right. You don't check b when you output 0 are right. But the whole thing is a little mysterious in what you are really trying to accomplish. Floating point comparisons between floats and doubles will have variations, minute, so you should compare with a delta 'acceptable' variation for your situation. I've always done this via inline functions that just perform the work (did it once with a macro, but thats too messy). Anyhow, yah, rounding issues abound with this type of example. Read the floating point stuff, and know that .7 is different than .7f and assigning .7 to a float will cast a double into a float, thus changing the exact nature of the value. But, the programming assumption about b being wrong since you checked a blared out to me, and I had to note that :)