March 5, 2004 ISINF 3

### NAME

isinf - test for infinity

### LIBRARY

Standard C Library (libc, -lc)

### SYNOPSIS

```int` isinf(```real-floating x`)

### DESCRIPTION

The isinf(``) macro determines whether its argument ```x` is an infinity (positive or negative). An argument represented in a format wider than its semantic type is converted to its semantic type first. The determination is then based on the type of the argument.

#### IEEE 754

It is determined whether the value of ```x` is an infinity.

#### VAX

Infinities are not supported.

### RETURN VALUES

The isinf(``) macro returns a non-zero value if the value of ```x` is an infinity. Otherwise 0 is returned.

### SEE ALSO

fpclassify(3), isfinite(3), isinff(3), isnan(3), isnanf(3), isnormal(3), math(3), signbit(3)

### STANDARDS

The isinf(``) macro conforms to ISO/IEC 9899:1999 (``ISO C99'') .