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;
}
?>
abs
说明
number abs ( mixed number )返回参数 number 的绝对值。如果参数 number 是 float，则返回的类型也是 float，否则返回 integer（因为 float 通常比 integer 有更大的取值范围）。
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User Contributed Notes
Josh
08-Jan-2006 08:06
08-Jan-2006 08:06
jeremys at hang dash wire dot com
13-Dec-2005 12:05
13-Dec-2005 12:05
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)/$x : 0 too, but might as well avoid the float division.
Lazarus
12-Dec-2005 10:53
12-Dec-2005 10:53
Even that is unnecessarily complex. Try this:
<?php
function n_abs($v) { return -abs($v) ; }
?>
Faster too.
rdk
11-Nov-2005 03:04
11-Nov-2005 03:04
concordia, you seem to be overcomplicating matters. If you want to do the reverse of the abs function, the only code required is:
<?php
function n_abs($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 ($num))" would make it function as indicated by your comments (i.e. toggle the sign bit), but it would still be overly complicated.
concordia at game dot xakep dot org
07-Nov-2005 05:35
07-Nov-2005 05:35
Sometimes you may want to do the opposite of abs(): turn a positive number into a negative.
<?php
function turn_neg ($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 03:05
11-Aug-2005 03:05
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.
$range = 1;
}
?>
Both ways seem smaller to me.
abodeman at y a h o o
25-May-2004 08:59
25-May-2004 08:59
There's another problem in the below code. The correct function to see whether a value is an integer is is_int(), not int(), so the code should look like this:
<?php
if(!is_numeric($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 05:59
02-Mar-2004 05:59
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 11:50
16-Jul-2003 11:50
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.