Positive and negative number values

Question

What is the best way to switch between a positive and negative value in a statement (in the example of a boolean):

myBoo = !myBoo

To do the same with an int I would need to check with if statement:

if (val >= 0)
{
     val = val*-1
}
else
{
    val = Math.abs(val);
}

is there a more direct way to do this?

Thanks in advance

If I understand correctly, you want negative numbers to be positive and positives to be negative... just multiple both by -1 — Lady_A, Jul 23 '18 at 16:03
Please look at this link https://stackoverflow.com/questions/1348080/convert-a-positive-number-to-negative-in-c-sharp — Rajkumar, Jul 23 '18 at 16:12

score 8 · Answer 1 · answered Jul 23 '18 at 16:03

8

int myBoo = 7;

myBoo = -myBoo;

answered Jul 23 '18 at 16:03

nvoigt

2

More efficient than multiplication afaik, so +1. – Perry Monschau Jul 23 '18 at 16:04
@PerryMonschau I think in practice that this wouldn't be more efficient, at least measurably so, an interesting benchmark to try out though. – DavidG Jul 23 '18 at 16:22
@DavidG I think this sort of benchmark would come down to the compiler used. Probably most are smart enough to compile both into the same operation, if I'm not mistaken. – Perry Monschau Jul 23 '18 at 16:25
@PerryMonschau Well I doubt they would compile to the same operation, at least not in C#. I just don't think the difference would be much, if anything. – DavidG Jul 23 '18 at 16:38
@DavidG Different code for different situations. If this operation takes place in the core process of an application and wants to run a million times a second, then every optimisation counts. – Perry Monschau Jul 23 '18 at 16:52
@PerryMonschau Yes, but I'm suggesting that even that won't matter. – DavidG Jul 23 '18 at 16:53
@DavidG like you said, an interesting benchmark to try out. – Perry Monschau Jul 23 '18 at 16:53
2

@PerryMonschau Well I tried it with 100 million iterations and that gave me a difference of 0.1s in total, second run it was the other way round. So not enough for most mortals to worry about :) – DavidG Jul 23 '18 at 17:03

score 0 · Answer 2 · answered Jul 23 '18 at 16:04

0

answered Jul 23 '18 at 16:04

Hemant Singh

Fuzzybear · Accepted Answer · 2018-07-23T20:38:37.387

0

One way would be to just add a negative sign in front of the value:

int myInt = -myInt;

Another way to switch between a positive or negative number in a statement would be to multiply it by -1.

myInt = myInt * -1;

edited Jul 23 '18 at 20:38

answered Jul 23 '18 at 16:04

Fuzzybear

score -2 · Answer 4 · answered Jul 23 '18 at 16:07

-2

You can use Math.signum(), it returns -1.0 if number is negative and 1.0 if it is positive, 0 if it is zero

answered Jul 23 '18 at 16:07

The person asking the question wants to negate the number. so for example given `1234` it would give you `-1234`. This does not answer the question at all. – DavidG Jul 23 '18 at 16:23

4 Answers4