```ISLESSEQUAL(3P)           POSIX Programmer's Manual          ISLESSEQUAL(3P)
```

## PROLOG         top

```       This manual page is part of the POSIX Programmer's Manual.  The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
```

## NAME         top

```       islessequal — test if x is less than or equal to y
```

## SYNOPSIS         top

```       #include <math.h>

int islessequal(real-floating x, real-floating y);
```

## DESCRIPTION         top

```       The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements described
here and the ISO C standard is unintentional. This volume of
POSIX.1‐2008 defers to the ISO C standard.

The islessequal() macro shall determine whether its first argument is
less than or equal to its second argument. The value of
islessequal(x, y) shall be equal to (x) <= (y); however, unlike
(x) <= (y), islessequal(x, y) shall not raise the invalid floating-
point exception when x and y are unordered.
```

## RETURN VALUE         top

```       Upon successful completion, the islessequal() macro shall return the
value of (x) <= (y).

If x or y is NaN, 0 shall be returned.
```

## ERRORS         top

```       No errors are defined.

The following sections are informative.
```

## EXAMPLES         top

```       None.
```

## APPLICATION USAGE         top

```       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 may 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 NaNs without suffering the invalid floating-point
exception. In the SYNOPSIS section, real-floating indicates that the
argument shall be an expression of real-floating type.
```

## RATIONALE         top

```       None.
```

## FUTURE DIRECTIONS         top

```       None.
```

```       isgreater(3p), isgreaterequal(3p), isless(3p), islessgreater(3p),
isunordered(3p)

The Base Definitions volume of POSIX.1‐2008, math.h(0p)
```

```       Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .