---
name: "islessgreater"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/isgreater"
---

# islessgreater(3)

compare two floating-point numbers

Part of [isgreater(3)](/isgreater/3.md).

## NAME

**isgreater**, **isgreaterequal**, **isless**, **islessequal**, **islessgreater**, **isunordered** – compare two floating-point numbers

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<math.h\>**

*int*\

**isgreater**(*real-floating x*, *real-floating y*);

*int*\

**isgreaterequal**(*real-floating x*, *real-floating y*);

*int*\

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

*int*\

**islessequal**(*real-floating x*, *real-floating y*);

*int*\

**islessgreater**(*real-floating x*, *real-floating y*);

*int*\

**isunordered**(*real-floating x*, *real-floating y*);

## DESCRIPTION

Each of the macros **isgreater**(), **isgreaterequal**(), **isless**(), **islessequal**(), and **islessgreater**() take arguments *x* and *y* and return a non-zero value if and only if its nominal relation on *x* and *y* is true. These macros always return zero if either argument is not a number (NaN), but unlike the corresponding C operators, they never raise a floating point exception.

The **isunordered**() macro takes arguments *x* and *y* and returns non-zero if and only if any of *x* or *y* are NaNs. For any pair of floating-point values, one of the relationships (less, greater, equal, unordered) holds.

## SEE ALSO

[fpclassify(3)](/fpclassify/3.md), [math(3)](/math/3.md), [signbit(3)](/signbit/3.md)

## STANDARDS

The **isgreater**(), **isgreaterequal**(), **isless**(), **islessequal**(), **islessgreater**(), and **isunordered**() macros conform to ISO/IEC 9899:1999 (“ISO C99”).

## HISTORY

The relational macros described above first appeared in FreeBSD 5.1.