Content-type: text/html Man page of isless

# isless

Section: Mathematical Library Functions (3M)
Updated: 12 Jul 2006

## NAME

isless - test if x is less than y

## SYNOPSIS

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

int isless(real-floating x, real-floating y);

## DESCRIPTION

The isless() macro determines whether its first argument is less than its second argument. The value of isless(x, y) is equal to (x) < (y); however, unlike (x) < (y), isless(x, y) does not raise the invalid floating-point exception when x and y are unordered.

## RETURN VALUES

Upon successful completion, the isless() macro returns the value of (x) < (y).

If x or y is NaN, 0 is returned.

## ERRORS

No errors are defined.

## USAGE

The relational and equality operators support the usual mathematical relationships between numeric values. For any ordered pair of numeric values, exactly one of the relationships (less, greater, and equal) is true. Relational operators can raise the invalid floating-point exception when argument values are NaNs. For a NaN and a numeric value, or for two NaNs, just the unordered relationship is true. This macro is a quiet (non-floating-point exception raising) version of a relational operator. It facilitates writing efficient code that accounts for quiet NaNs without suffering the invalid floating-point exception. In the SYNOPSIS section, real-floating indicates that the argument is an expression of real-floating type.

## ATTRIBUTES

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

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

isgreater(3M), isgreaterequal(3M), islessequal(3M), islessgreater(3M), isunordered(3M), math.h(3HEAD), attributes(5), standards(5)

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUES
ERRORS
USAGE
ATTRIBUTES