PROLOGThis 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.
NAMEhypot, 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);
DESCRIPTIONThe 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
2without 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 VALUEUpon 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.
ERRORSThese 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.
- 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.
EXAMPLESSee the EXAMPLES section in atan2().
APPLICATION USAGEhypot(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.
SEE ALSOatan2(), feclearexcept(), fetestexcept(), isnan(), sqrt() The Base Definitions volume of POSIX.1-2008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, <math.h>
COPYRIGHTPortions 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 www.unix.org/online.html .
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