PHP: abs - Manual

abs

Josh
07-Jan-2006 04:06


Let's say you are resizing images to a standard size that can be expressed as a ratio (width/height). The problem I came into was that I wanted to be reasonable with the proportion of the images that my customer is uploading (couldn't we all use a little less horizontal on pictures?), but I wanted to reject the horizontal pictures when they were uploading vertical ones. So I wanted to accept proportions of images that were within a reasonable threshold (+ or -) of what I will be resizing them to.



Assuming a standard of 1 to 4 (0.25) and a threshold of no more than 0.05 deviation, then the number 0.30 and 0.20 would return true and 0.19 would return false.



<?php 



function threshold($given,$thresh,$standard)

{

     return (abs($given-$standard)<=$thresh) ? true : false;

}



?>

jeremys at hang dash wire dot com
12-Dec-2005 08:05


I'm unable to replicate concordia's problem with the $n = $n - $n * 2 code.  I agree with the simplification to $n *= -1.  But there's no reason that concordia's code should return 6 for the value -2, and it doesn't appear to.  When I tried it, PHP returned 2, as it should.  If PHP were somehow flipping the sign of integers randomly, that would be a *major* bug!



There doesn't seem to be a sgn() function yet.  Here's some quick code to do it:



function sgn($x) {

   return $x ? ($x>0 ? 1 : -1) : 0;

}



You could use $x ? abs($x)/$x : 0 too, but might as well avoid the float division.

Lazarus
12-Dec-2005 06:53


Even that is unnecessarily complex. Try this:



<?php



function n_abs($v) { return -abs($v) ; }



?>



Faster too.

rdk
10-Nov-2005 11:04


concordia, you seem to be overcomplicating matters.  If you want to do the reverse of the abs function, the only code required is:



<?php



function n_abs($num) {

    return ($num > 0) ? $num * -1 : $num;

}



n_abs(2); //-2

n_abs(-2); //-2



?>



If you want to switch the sign bit of a number, as your example seems to indicate...

turn_neg (2); // -2

turn_neg (-2); // 2

...you just need to do $num *= -1;



Your function also doesn't seem to work. Switching "if (is_neg ($num))" to "if (!is_neg ($num))" would make it function as indicated by your comments (i.e. toggle the sign bit), but it would still be overly complicated.

concordia at game dot xakep dot org
06-Nov-2005 01:35


Sometimes you may want to do the opposite of abs(): turn a positive number into a negative.



<?php



function turn_neg ($num) {

    return $num - $num * 2;

}



?>



But this can create errors when you put a negative number inside...



turn_neg (-2) returns 6.

  

<?php



turn_neg (-2); // 6.



?>



The solution is to make another function to determine if the number is negative or not.



<?php



function is_neg ($num) {

   return $num < 0;

}



function turn_neg ($num) {

    if (is_neg ($num)) {

       return $num - $num * 2;

    } else {

       return abs ($num);

    }

}



turn_neg (2); // -2

turn_neg (-2); // 2



?>



Or, if the number is not negative, you could also return false.

alreece45 at yahoo dot com
10-Aug-2005 12:05


Both of the below codes were wrong.



<?php



// Check to see if $range is numberic, if not, set it to the integer value 1



if(!is_numeric($range)) {



 $range=1;



}



// Check to see if $range is an integer and not a float. Use is_int() and not int().



if(!is_int($range)) {



// Make it an integer. Use intval() here, not int_val.



 $range=intval($range);



}



$range=abs($range);



?>



The only thing I don't get is why we have to check before doing the functions. Whether or not we do the functions it will give us what we want. The only check I really understand being there is the one that sets it to one.



Why not just do:



<?php



// If $range is numberic, make it in positive integer, otherwise, make it one.



$range = is_numeric($range) ? abs(intval($range)) : 1;



?>



Seems like a lot less code. Or If you prefer to stay with if statements:



<?php



if(is_numberic($range)) {



 // If $range is numberic, make it in positive integer.



 $range = abs(intval($range));



}



else {



 //otherwise, make it one.



 $range = 1;



}



?>



Both ways seem smaller to me.

abodeman at y a h o o
24-May-2004 05:59


There's another problem in the below code. The correct function to see whether a value is an integer is is_int(), not int(), so the code should look like this:



<?php 

if(!is_numeric($range))//checks for numeric input 

{ 

$range=1; 

}//sets $range to integer 1 if input is anything other than a numeric value 

if(!is_int($range))//checks to make sure it is an integer (not decimal) 

{ 

$range=int_val($range); 

}//if a decimal- sets $range to integer value 

$range=abs($range);//sets value to positive whole number 

?>

mbender at duforu dot com
01-Mar-2004 01:59


In reference to the previous code sample the int_val function is actually intval() [http://us4.php.net/manual/en/function.intval.php]:



<?php 

if(!is_numeric($range))//checks for numeric input 

 { 

  $range=1; 

 } //sets $range to integer 1 if input is anything other than a numeric value 

if(!int($range))//checks to make sure it is an integer (not decimal) 

 { 

 $range=intval($range) // not ->  int_val($range); 

 }//if a decimal- sets $range to integer value 

$range=abs($range);//sets value to positive whole number 

?>

bgustin AT trukfixer DOT com
16-Jul-2003 08:50


assume we take user input from a form untreated and assign it to variable $range. We want to be sure this number is a Positive Whole number, since abs() just sets a number to positive or 0, and we dont want decimals...





<?php


if(!is_numeric($range))//checks for numeric input


{


$range=1;


}//sets $range to integer 1 if input is anything other than a numeric value


if(!int($range))//checks to make sure it is an integer (not decimal)


{


$range=int_val($range);


}//if a decimal- sets $range to integer value


$range=abs($range);//sets value to positive whole number


?>





for example the input "testing" would return $range =1,


the input "3.578" would return value=3


If the input is null, I am havent tested to see if it gets set to 1 courtesy of int_val or not, but I believe it will be.





I'm sure there's probably a more elegant way to do this using regex, however for an apprentice php coder, this might be a little easier to understand and use.

abs

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