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.

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hypot, hypotf, hypotl - Euclidean distance function

#include <math.h>

double hypot(doublex, doubley);

float hypotf(floatx, floaty);

long double hypotl(long doublex, long doubley);

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

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(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

xandy.If the correct value would cause overflow, a range error shall occur and

hypot(),hypotf(), andhypotl() shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.If

xoryis ±Inf, +Inf shall be returned (even if one ofxoryis NaN).If

xoryis 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:

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

Range Error The result overflows. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errnoshall 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. errnoshall 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.

None.

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

hypot(x, ±0) is equivalent tofabs(x).Underflow only happens when both

xandyare 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.

feclearexcept() ,fetestexcept() ,isnan() ,sqrt() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions,<math.h>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .

IEEE/The Open Group |
HYPOT (P) | 2003 |