Division fuctions

Marc Glisse marc.glisse at inria.fr
Thu Apr 28 08:02:27 CEST 2011

On Thu, 28 Apr 2011, Dimitri wrote:

> I've just read http://gmplib.org/manual/Integer-Division.html and I don't
> understand why there is three cathegories of functions (cdiv, fdiv and tdiv).
> Maybe it's because of my bad english, but I can't understand what thoses
> sentences means.

Seems quite well explained to me, but in case, a different explanation:

when you divide 6/2, the result is 3, no problem. When you divide 5/2, the 
answer would be 2.5, but we are working with integers, so we need to round 
2.5 to an integer. If you look at the libc functions to do that, you have 
ceil, floor and trunc. So gmp also provides 3 divisions, depending on the 
type of rounding you want.

Several roundings are useful. With 5 socks, you can only make 2 pairs. But 
you need 3 double-rooms to fit 5 people.

The third rounding only differs for negative numbers.

Marc Glisse

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