//Not for working with float
//anyways, seems cool for integers
//This works, iff is_int($num)
function nabs ($num=NULL){
$num = (int)$num;
if ($num<=0) return 0; //why bother bit flipping with 0
return ~$num + 1;
}
abs
(PHP 4, PHP 5)
abs — 絶対値
パラメータ
- number
-
処理する数値。
返り値
number の絶対値を返します。もし number の型が float であった場合、 返り値の型も float となります。それ以外の場合は 返り値の型は integer となります（float は、 integer の最大値より大きい値をとることがありえるからです）。
例
例1 abs() の例
<?php
$abs = abs(-4.2); // $abs = 4.2; (double/float)
$abs2 = abs(5); // $abs2 = 5; (integer)
$abs3 = abs(-5); // $abs3 = 5; (integer)
?>
abs
estoesunapija at hotmail dot com
27-Mar-2008 07:29
27-Mar-2008 07:29
thomas at tgohome dot com
30-Dec-2007 08:00
30-Dec-2007 08:00
If we want to into a war about speed with negative absolute numbers, I think bitwise operations should just about do it.
<?php
function n_abs($v) { return ~abs($v) + 1; }
?>
A NOT operation on any number with a sign bit will produce the negative of that number minus one. All we need to do is add one. Voila!
Speed test results (30000 iterations of various methods) produced very close dueling between the previous suggested method. Although I am on an overloaded Windows PC so I'm no benchmark, and I'll leave it up to you, the reader of this message.
Josh
08-Jan-2006 09:06
08-Jan-2006 09:06
Let's say you are resizing images to a standard size that can be expressed as a ratio (width/height). The problem I came into was that I wanted to be reasonable with the proportion of the images that my customer is uploading (couldn't we all use a little less horizontal on pictures?), but I wanted to reject the horizontal pictures when they were uploading vertical ones. So I wanted to accept proportions of images that were within a reasonable threshold (+ or -) of what I will be resizing them to.
Assuming a standard of 1 to 4 (0.25) and a threshold of no more than 0.05 deviation, then the number 0.30 and 0.20 would return true and 0.19 would return false.
<?php
function threshold($given,$thresh,$standard)
{
return (abs($given-$standard)<=$thresh) ? true : false;
}
?>
jeremys at hang dash wire dot com
13-Dec-2005 01:05
13-Dec-2005 01:05
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)/$x : 0 too, but might as well avoid the float division.
Lazarus
12-Dec-2005 11:53
12-Dec-2005 11:53
Even that is unnecessarily complex. Try this:
<?php
function n_abs($v) { return -abs($v) ; }
?>
Faster too.
rdk
11-Nov-2005 04:04
11-Nov-2005 04:04
concordia, you seem to be overcomplicating matters. If you want to do the reverse of the abs function, the only code required is:
<?php
function n_abs($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 ($num))" would make it function as indicated by your comments (i.e. toggle the sign bit), but it would still be overly complicated.
concordia at game dot xakep dot org
07-Nov-2005 06:35
07-Nov-2005 06:35
Sometimes you may want to do the opposite of abs(): turn a positive number into a negative.
<?php
function turn_neg ($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
11-Aug-2005 04:05
11-Aug-2005 04:05
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.
$range = 1;
}
?>
Both ways seem smaller to me.
abodeman at y a h o o
25-May-2004 09:59
25-May-2004 09:59
There's another problem in the below code. The correct function to see whether a value is an integer is is_int(), not int(), so the code should look like this:
<?php
if(!is_numeric($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
02-Mar-2004 06:59
02-Mar-2004 06:59
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
17-Jul-2003 12:50
17-Jul-2003 12:50
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.