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is_nan

darkangel at moveinmod dot net
01-Mar-2006 10:04


nan/"not a number" is not meant to see if the data type is numeric/textual/etc..



NaN is actually a set of values which can be stored in floating-point variables, but dont actually evaluate to a proper floating point number.



The floating point system has three sections: 1 bit for the sign (+/-), an 8 bit exponent, and a 23 bit fractional part.

There are rules governing which combinations of values can be placed into each section, and some values are reserved for numbers such as infinity. This leads to certain combinations being invalid, or in other words, not a number.

Sku
04-Dec-2005 01:29


Hi nez,



better would be:



function isNaN( $var ) {

     return !ereg ("^[-]?[0-9]+([\.][0-9]+)?$", $var);

}



ys, Sku

nez [at] NOSPAM gazeta [dot] pl
26-Sep-2005 01:27


Paul, i guess better would be:



function isNaN( $var ) {

     return ereg ("^[-]?[0-9]+([\.][0-9]+)?$", $var);

}

Vincent
23-Feb-2005 06:04


Since NaN is not even equal to itself, here is a way to test it:



<?php



function my_is_nan($_) {

return ($_ !== $_);

}



?>

paul at NOSPAM dot paultastic dot com
10-Jun-2002 11:55


See is_numeric if you have an older version of PHP than 4.20.  It should serve your purpose well.



If you're using PHP 3, you can use a regular expression:



function isNaN( $var ) {

     return ereg ("^[0-9\.]+$", $var); 

}

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