Can I count on -0 ?

Programming Questions

doodle

in Programming Questions • 3 years ago

I am doing the slope equation of a straight line and there are of course 2 special cases involved where the line is vertical and and where the line is horizontal. When the line is horizontal Vertical I was trying to figure out a proper return would be to trigger handling this special case.

I don't really know what the return of Infinity represents,is it a generic Java return or Processing specific?

I would like to keep the function as platform generic as possible.

In the special cause where the denominator is 0 if I can return -0 and let that represent the special case of a horizontal line. Will this also work in C?

Replies(8)

bjordal

Re: Can I count on -0 ?

3 years ago

im not really sure on how to respond to this...
as far as i know there is no such thing as negative zero, on a related note if there was such a thing would -0 < 0 (negative nothing is smaller than nothing)?

But when it comes to the line being horizontal. 0 is actually it's slope so there's nothing you need to worry about there. Your problem is however when you got a vertical line because then the question is, is the slope infinity or negative infinity? :)

also i totally lol'd at println(1/0.000000000000000000000000000000000000001); => "Infinity"
finally we have a fixed value of infinity

doodle

Re: Can I count on -0 ?

3 years ago

I was assuming that a negative number had a bit flag set to denote that it was negative and that - zero was simply 0 with the flag set to negative. I need to return something to denote that the special case of a vertical line has been encountered.

Mathematically of course this all equates to a bunch of nonsense.

float slope(float x1 , float y1, float x2 , float y2 ){
if( x1-x2 != 0){
result = ( (y1 - y2) / (x1 -x2) );
return result;
}
else{return -0;}

doodle

Re: Can I count on -0 ?

3 years ago

Nope thats not how it works all.

When you divide by zero Processing returns infinity. You can't test against this as a string. I could just make cases of vertical lines have a slope of a really silly decimal point and this wouldn't really affect calculation. Other people must have a function for calculating slope, how did other people handle this?