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arithmetic condition

Started by Luya Jan 4, 2003 at 2:02 AM 7 replies 450+ views

Original Post

Jan 4, 2003 at 2:02 AM

6 tutorials later, I noticed some codes that can be easily by a single line code. This code is the arithmetic condition. For those who forgot the definition, it is like the normal if...else condition with a difference: it''s written like

(condition?true:false);

for those who know algebra this example will help

(a > b?a:b);

. The equivalent is

  
if(a > b)
{return a;}
else
{return b;}

It is possible to use the function to return value. Let''s take the look on this example from lesson 7:

  
if (!light)				// If Not Light

{
    glDisable(GL_LIGHTING);		// Disable Lighting

}
else					// Otherwise

{
    glEnable(GL_LIGHTING);		// Enable Lighting	

}

The equivalent is

(!light?glDisable(GL_LIGHTING):glEnable(GL_LIGHTING));

. Don''t forget to add this library: #include <math.h>. Use it wisely

joanusdmentia

Jan 4, 2003 at 3:28 AM

You don''t need math.h to use ?: it''s just part of the language.

CraZeE

Jan 4, 2003 at 3:37 AM

oh, and its called a ternary operator.. the one and only kind of it in C/C++. not sure of its existence in other languages.

Fruny

Jan 4, 2003 at 3:45 AM

a few corrections and additions.

- Using the ternary operator doesn''t require <math.h>, it is a built-in. If you''re using C++, it is better to include <cmath> than <math.h>. Also note it is a header, not a library

- Be careful when using it with functions returning void. And in the general case, the types of the true-expression and the false-expression must be compatible.
- The ternary operator can be used in expressions, not just statements : printf( "You have %s", win?"won":"lost" ); (won?account:jackpot) += 100; and so on...

Not that it''s always a good idea to use it...

titan2782

Jan 4, 2003 at 11:27 AM

it is not recommended. I''ve read 3 books that explain it and how to use it, but they all say to not use it.

IT Administrator / Software Engineere
http://drdsoftware.cjb.net

Luya

Jan 5, 2003 at 1:57 AM

Oooops, it''s true. is a header file. First time I hear about . I would like to know more about the non-recommended use of ternary operator.

wild_pointer

Jan 5, 2003 at 3:42 AM

What makes more sense in a tutorial?


if (!light)				// If Not Light
{       
    glDisable(GL_LIGHTING);		// Disable Lighting}
else					// Otherwise
{    
    glEnable(GL_LIGHTING);		// Enable Lighting	
}


(!light?glDisable(GL_LIGHTING):glEnable(GL_LIGHTING));

You can cram anything you want onto one line. Hey, why have whitespace at all, right?

Beer Hunter

Jan 5, 2003 at 3:52 AM

Pouya''s tetris tutorial, page 2

Crispy

Jan 5, 2003 at 8:01 AM

personal recommendation: only use the ?: operator in inlined functions such as:


int TPerson::GetSomeFactor()
{
  return(PersonType == PT_WOMAN ? (Age * Weight / Factor) : ((Age * Weight + SecretSize) / Factor));
}

Other than that, it's best to use the if...else block for the sake of readability.

Crispy

EDIT: missing parenthesis

[edited by - crispy on January 5, 2003 9:04:33 AM]

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