IEEE Std 1003.1-2024
Copyright © 2001-2024 The IEEE and The Open Group
NAME
hypot, hypotf, hypotl — Euclidean distance function
SYNOPSIS
#include <math.h>double hypot(double
x , double y );
float hypotf(float x , float y );
long double hypotl(long double x , long double y );
DESCRIPTION
[CX]
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.1-2024 defers to the ISO C standard.
These functions shall compute the value of the square root of x2+y2 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.
![[Option End]](https://pubs.opengroup.org/onlinepubs/9799919799/images/opt-end.gif)
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.
[MX]
If x or y is NaN, and the other is not ±Inf, a NaN shall be returned.
[MXX]
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
- [MX]
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()
XBD 4.23 Treatment of Error Conditions for Mathematical Functions, <math.h>
CHANGE HISTORY
First released in Issue 1. Derived from Issue 1 of the SVID.
Issue 5
The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.
Issue 6
The hypot() function is no longer marked as an extension.
The hypotf() and hypotl() functions are added for alignment with the ISO/IEC 9899:1999 standard.
The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 standard.
IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.
IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/49 is applied, updating the EXAMPLES section.
Issue 7
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0273 [68] is applied.
End of informative text.
return to top of page
UNIX® is a registered Trademark of The Open Group.
POSIX™ is a Trademark of The IEEE.
Copyright © 2001-2024 The IEEE and The Open Group, All Rights Reserved
[ Main Index | XBD | XSH | XCU | XRAT ]