[erlang-bugs] error in rem operator

Daniel Luna <>
Thu May 10 09:44:45 CEST 2007


On Thu, 10 May 2007, Jay Anderson wrote:
> I think I may have found a bug. Here's my factorial function:
>
> /////
> -module(fact).
> -export([fact/1]).
>
> fact(N) -> fact(N,1).
> fact(0,P) -> P;
> fact(N,P) -> fact(N-1,P*N).
> /////
>
> Now from the shell I did this:
>
> c(fact).
> X = fact:fact(1000).
> X rem 823543. %7^7=823543
>
> This incorrectly gives 823543 instead of 0. Thanks!

There is something very strange going on here.

Look at the result of:

X div 823543.

48860503.....9999999999999

823543 is a factor of X, so X is evenly divisible by 823543. That means 
that the rest of the prime factors in X should still be there. I am 
missing a whole lot of 0s.

(Tested on R11B-2)

/Luna
-- 
Daniel Luna                           | Top reasons that I have a beard:
                     |  a) Laziness.
http://www.update.uu.se/~luna/        |  b) I can.
Don't look at my homepage (it stinks).|  c) I can get away with it.



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