int -- floor or ceiling? (C Programming)

smoothdogg00 · 04-16-2006, 07:48 PM

When an int is divided by another int and stored, (int x = y/z: int x = 5/3) does it floor or ceiling, or does it depend on the outcome? Would x be 1 or 2?

95se · 04-16-2006, 08:14 PM

Think of it as always chopping off the decimal point, so floor

haymaker2000 · 04-16-2006, 08:15 PM

I could be wrong, but I think it floors. I'm actually quite sure about this, because if you do modulo arithmetic, you always get the remainder.
So, 6/4 would give you 1 remainder 2. The remainder can be calculated using 6%4 (=2). So, in general a%b = r (a,b integers).

primo · 04-17-2006, 02:34 AM

Quoting from: http://home.tiscalinet.ch/t_wolf/tw/c/c9x_changes.html

Quote:

The integer division and modulus operators are defined to perform truncation towards zero. (In C89, it was implementation-defined whether truncation was done towards zero or -infinity. This is (obviously) important only if one or both operands are negative. Consider:

-22 / 7 = -3
-22 % 7 = -1

truncation towards zero

-22 / 7 = -4
-22 % 7 = 6

truncation towards -infinity

Both satisfy the required equation (a/b)*b + a%b == a. The second has the advantage that the modulus is always positive -- but they decided on the other (more Fortran-like, less Pascal-like) variant...)