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HP-UX 11i Version 3: February 2007

Technical documentation

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isfinite() — floating-point finiteness macro


#include <math.h>

int isfinite( floating-type x);


The isfinite() macro determines whether its argument has a finite value (zero, denormalized, or normalized, and not infinite or NaN). The argument must be of floating type, and classification is based on the type of the argument. For HP Integrity servers, the argument can be any floating type. For PA-RISC, the argument must be either double or float.

The isfinite() macro implements the finite() functionality recommended by the IEEE-754 standard for floating-point arithmetic.


To use the isfinite() macro, compile either with the default -Ae option or with the -Aa and -D_HPUX_SOURCE options. Make sure your program includes <math.h>. Link in the math library by specifying -lm on the compiler or linker command line.


The isfinite() macro returns a nonzero value if and only if its argument has a finite value. The macro raises no floating-point exceptions.


No errors are defined.


Make sure a value is finite before continuing operations on it:

#include <math.h> /*...*/ float x; /*...*/ if (isfinite(x)) /*...*/


isfinite(): ISO/IEC C99

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