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table of contents

HYPOT(3P) | POSIX Programmer's Manual | HYPOT(3P) |

# PROLOG¶

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¶

hypot, hypotf, hypotl — Euclidean distance function

# SYNOPSIS¶

#include <math.h>

double hypot(doublex, doubley); float hypotf(floatx, floaty); long double hypotl(long doublex, long doubley);

# DESCRIPTION¶

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.1‐2017 defers to the ISO C standard.

These functions shall compute the value of the square root of
*x*2+*y*2 without undue overflow or underflow.

An application wishing to check for error situations should set
*errno* to zero and call *feclearexcept*(FE_ALL_EXCEPT) before
calling these functions. On return, if *errno* is non-zero or
*fetestexcept*(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.

# RETURN VALUE¶

Upon successful completion, these functions shall return the
length of the hypotenuse of a right-angled triangle with sides of length
*x* and *y*.

If the correct value would cause overflow, a range error shall
occur and *hypot*(), *hypotf*(), and *hypotl*() shall return
the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.

If *x* or *y* is ±Inf, +Inf shall be returned
(even if one of *x* or *y* is NaN).

If *x* or *y* is NaN, and the other is not ±Inf,
a NaN shall be returned.

If both arguments are subnormal and the correct result is subnormal, a range error may occur and the correct result shall be returned.

# ERRORS¶

These functions shall fail if:

- Range Error
- The result overflows.

If the integer expression (*math_errhandling* &
MATH_ERRNO) is non-zero, then *errno* shall be set to **[ERANGE]**.
If the integer expression (*math_errhandling* & MATH_ERREXCEPT) is
non-zero, then the overflow floating-point exception shall be raised.

These functions may fail if:

- Range Error
- The result underflows.

If the integer expression (*math_errhandling* &
MATH_ERRNO) is non-zero, then *errno* shall be set to **[ERANGE]**.
If the integer expression (*math_errhandling* & MATH_ERREXCEPT) is
non-zero, then the underflow floating-point exception shall be raised.

*The following sections are informative.*

# EXAMPLES¶

See the EXAMPLES section in *atan2*().

# APPLICATION USAGE¶

*hypot*(*x*,*y*), *hypot*(*y*,*x*),
and *hypot*(*x*, -*y*) are equivalent.

*hypot*(*x*, ±0) is equivalent to
*fabs*(*x*).

Underflow only happens when both *x* and *y* are
subnormal and the (inexact) result is also subnormal.

These functions take precautions against overflow during intermediate steps of the computation.

On error, the expressions (*math_errhandling* &
MATH_ERRNO) and (*math_errhandling* & MATH_ERREXCEPT) are
independent of each other, but at least one of them must be non-zero.

# RATIONALE¶

None.

# FUTURE DIRECTIONS¶

None.

# SEE ALSO¶

* atan2()*,

*,*

*feclearexcept*()*,*

*fetestexcept*()*,*

*isnan*()

*sqrt*()The Base Definitions volume of POSIX.1‐2017, *Section
4.20*, *Treatment of Error Conditions for Mathematical Functions*,
**<math.h>**

# COPYRIGHT¶

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

2017 | IEEE/The Open Group |