From: "Mike T. Miller" <mtm@...>
Date: 2001-05-08T04:40:48+09:00
Subject: [ruby-talk:14802] Re: Integer division oddness

In partial answer to my own post, I just found this
link: http://xenia.media.mit.edu/~bdenckla/thesis/texts/htthe/node13.html

It still seems wrong to me.  Which is right? -1 or -2?
I guess it boils down to whether or not you believe that the
modulus can be negative.


" My father pointed out this oddity.
" 
" Using integer math, try this on various languages:
" 
" -10 / 9
" 
" For ruby, python and tcl you get: -2!
" For java, c and gforth you get:   -1
" 
" Getting -2 seems really wrong to me.  I looked at the
" code for ruby and found this: (numeric.c: line 1056)
" 
"     if ((mod < 0 && y > 0) || (mod > 0 && y < 0)) {
"         mod += y;
"         div -= 1;
"     }
" 
" So, bascially, one is subtracted on purpose in this case.
" Is this an accepted way to do integer division tha I'm not
" familiar with?
" 
" thanks,
" Mike