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***drdebcol*** · (This post was last modified: 03-18-2010 04:03 AM by drdebcol.)

This is an interesting and simple function which i haven't found in any of programming languages. It is easy to make so i decided to make it.
In mathematics, the sign function is an odd mathematical function that extracts the sign of a real number.
Here is the mathematical definition :
[Image: 45159_sigumfunctiondefinition.jpg]

[Image: 45159_sigumfunctiondefinition.jpg]

And you can find signum by using this formula :
[Image: 45160_sigumfunctiondefinition2.jpg]

As you can see it is defined for every x from set of real numbers.
And you can see that on this graphic :
[Image: 45161_signumfunctiongraphic.jpg]

So it is mathematically simple, and in programming it is also easy to make.
So here is the code in Pascal :

Code:

function sgn(x:real):shortint;

begin

  if x=0 then

    sgn:=0

  else

    if x>0 then

      sgn:=1

    else

      sgn:=-1;

end;

And C & C++ code :

Code:

short sgn(float x)

{

  if (x==0)

    return 0;

  else

    if (x>0)

      return 1;

    else

      return -1;     

}

I used shortint type in both of languages, just to save memory.
Basically it returns only 3 states (1,0,-1), so you can't use bool, but you can save memory by using shortint.
I hope that you learned something from this, it can't be more simple !
And yeah, you can find more about it here on Wikipedia :
http://en.wikipedia.org/wiki/Sign_function

***l3g1sl4tor*** · 03-12-2010, 09:39 PM

hehe... interesting issue... I think i used something similar for one task of class all negative and positive numbers from one array in 2 other... If I find source, i will post it Smile

Good point DrDebcol! Smile

***drdebcol*** · 03-12-2010, 09:52 PM

(03-12-2010 09:39 PM)l3g1sl4tor Wrote: hehe... interesting issue... I think i used something similar for one task of class all negative and positive numbers from one array in 2 other... If I find source, i will post it Good point DrDebcol!

Yeah this can be useful.
I noticed that i forgot to mark 1 and -1 on graphic, but it is obvious !

***l3g1sl4tor*** · 03-13-2010, 07:13 AM

Oh well... first i have looked is formula and program, so i didnt noticed also Smile