HYPOT(3) Library Functions Manual HYPOT(3)

hypot hypotf hypotl — Euclidean distance function

#include <math.h>

double hypot(double x, double y);
float hypotf(float x, float y);
long double hypotl(long double x, long double y);

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.

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 (FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or (FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

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 is returned.

These functions shall fail if:

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:

[MX] 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.

See the EXAMPLES section in atan2(3).

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

hypot ( x, ±0) is equivalent to ( 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.

None.

None.

atan2(3) , feclearexcept(3) , fetestexcept(3) , isnan(3) , sqrt(3)

XBD V1_chap04(7) , <math.h>

First released in Issue 1. Derived from Issue 1 of the SVID.

The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

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 (“ISO C99”) standard.

The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 (“ISO C99”) standard.

IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 (“ISO C99”) standard are marked.

IEEE Std 1003.1-2001 (“POSIX.1”)/Cor 2-2004, item XSH/TC2/D6/49 is applied, updating the EXAMPLES section.

January 1, 2008 posix.fail