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isinf(), isinff()

Test for infinity

Synopsis:

#include <math.h>

int isinf ( double x );

int isinff ( float x );

Arguments:

x

The number that you want to test.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

The isinf() and isinff() functions test to see if a number is "infinity."

Returns:

1

The value of x is infinity.

=/= 1

The value of x isn't infinity.

Examples:

#include <stdio.h>
#include <errno.h>
#include <inttypes.h>
#include <math.h>
#include <fpstatus.h>

int main(int argc, char** argv) 
{
    double a, b, c, d;

    a = 2;
    b = -0.5;
    c = NAN;
    fp_exception_mask(_FP_EXC_DIVZERO, 1);
    d = 1.0/0.0;
    printf("%f is %s \n", a,
           (isinf(a)) ? "infinite" : "not infinite");
    printf("%f is %s \n", b,
           (isinf(b)) ? "infinite" : "not infinite");
    printf("%f is %s \n", c,
           (isinf(c)) ? "infinite" : "not infinite");
    printf("%f is %s \n", d,
           (isinf(d)) ? "infinite" : "not infinite");

    return(0);
}

produces the output:

2.000000 is not infinite
-0.500000 is not infinite
NAN is not infinite
Inf is infinite

Classification:

isinf() is ANSI, POSIX 1003.1; isinff() is Unix

See also:

finite(), isnan()