sgn()

[notquitehere188]

Does anyone know the equivalent of the sgn() function found in vb for c
the function that returns -1 for negative numbers 0 for 0 and 1 for positive numbers. It is really useful for me in vb, also, would you caution aginst using it because of performance? every .1 milisecond is important in my program

i am just assuming that c# is the same as c

[jmcilhinney]

You could use

-(0.0).CompareTo(someNumber)

Doing anything 10000 times a second is likely to have an impact on performance.

[penagate]

Probably the most efficient way:

int Sgn(int val)
{
    return val < 0 ? -1 : 1;
}

Although, you should just inline the check into your code, instead of relying on checking the return value of a function (which is a branch in itself). It's not worth a function at all.

[penagate]

for c

Do you mean C, or C#? They are not the same, in fact they are very different animals. Although the snippet I provided will work in either language, jmcilhinney's will only work in C#.

There is a C/C++ forum further down the index page which is where you should post C questions.

[jmcilhinney]

I think you have to change your code to this penagate:

return val < 0 ? -1 : (val > 0 ? 1 : 0)

I don't think the parentheses are needed but they probably help with clarity anyway.

[penagate]

My bad. Forgot about zero

Here is yet another method.

return (val & 0xf0000000) > 0 ? -1 : val == 0 ? 0 : 1;

That one will also work in C.