is_nan(3) [php man page]

IS_NAN(3)								 1								 IS_NAN(3)

is_nan - Finds whether a value is not a number

SYNOPSIS

       bool is_nan (float  $val)

DESCRIPTION

	Checks whether $val is 'not a number', like the result of acos(1.01).

PARAMETERS

	      o $val
		- The value to check

RETURN VALUES

	Returns TRUE if $val is 'not a number', else FALSE.

EXAMPLES

       Example #1

	      is_nan(3) example

	      <?php
	      // Invalid calculation, will return a
	      // NaN value
	      $nan = acos(8);

	      var_dump($nan, is_nan($nan));
	      ?>

	      The above example will output:

	      float(NAN)
	      bool(true)

SEE ALSO

       is_finite(3), is_infinite(3).

PHP Documentation Group 														 IS_NAN(3)

nan(3M) 						  Mathematical Library Functions						   nan(3M)

NAME

       nan, nanf, nanl - return quiet NaN

SYNOPSIS

       c99 [ flag... ] file... -lm [ library... ]
       #include <math.h>

       double nan(const char *tagp);

       float nanf(const char *tagp);

       long double nanl(const char *tagp);

DESCRIPTION

       The function call nan("n-char-sequence") is equivalent to:

	 strtod("NAN(n-char-sequence)", (char **) NULL);

       The function call nan(" ") is equivalent to:

	 strtod("NAN()", (char **) NULL)

       If tagp does not point to an n-char sequence or an empty string, the function call is equivalent to:

	 strtod("NAN", (char **) NULL)

       Function calls to nanf() and nanl() are equivalent to the corresponding function calls to strtof() and strtold(). See strtod(3C).

RETURN VALUES

       These functions return a quiet NaN.

ERRORS

       No errors are defined.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       math.h(3HEAD), strtod(3C), attributes(5), standards(5)

SunOS 5.11							    12 Jul 2006 							   nan(3M)