1HYPOT(3P)                  POSIX Programmer's Manual                 HYPOT(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       hypot, hypotf, hypotl — Euclidean distance function
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SYNOPSIS

15       #include <math.h>
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17       double hypot(double x, double y);
18       float hypotf(float x, float y);
19       long double hypotl(long double x, long double y);
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DESCRIPTION

22       The functionality described on this reference page is aligned with  the
23       ISO C  standard.  Any  conflict between the requirements described here
24       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
25       defers to the ISO C standard.
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27       These  functions  shall  compute  the value of the square root of x2+y2
28       without undue overflow or underflow.
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30       An application wishing to check for error situations should  set  errno
31       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
32       functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
33       FE_DIVBYZERO  |  FE_OVERFLOW  | FE_UNDERFLOW) is non-zero, an error has
34       occurred.
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RETURN VALUE

37       Upon successful completion, these functions shall return the length  of
38       the hypotenuse of a right-angled triangle with sides of length x and y.
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40       If  the  correct  value would cause overflow, a range error shall occur
41       and hypot(), hypotf(), and hypotl() shall return the value of the macro
42       HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
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44       If  x  or  y  is ±Inf, +Inf shall be returned (even if one of x or y is
45       NaN).
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47       If x or y is NaN, and the other is not ±Inf, a NaN shall be returned.
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49       If both arguments are subnormal and the correct result is subnormal,  a
50       range error may occur and the correct result shall be returned.
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ERRORS

53       These functions shall fail if:
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55       Range Error The result overflows.
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57                   If  the  integer expression (math_errhandling & MATH_ERRNO)
58                   is non-zero, then errno shall be set to [ERANGE].   If  the
59                   integer  expression  (math_errhandling & MATH_ERREXCEPT) is
60                   non-zero, then the overflow floating-point exception  shall
61                   be raised.
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63       These functions may fail if:
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65       Range Error The result underflows.
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67                   If  the  integer expression (math_errhandling & MATH_ERRNO)
68                   is non-zero, then errno shall be set to [ERANGE].   If  the
69                   integer  expression  (math_errhandling & MATH_ERREXCEPT) is
70                   non-zero, then the underflow floating-point exception shall
71                   be raised.
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73       The following sections are informative.
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EXAMPLES

76       See the EXAMPLES section in atan2().
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APPLICATION USAGE

79       hypot(x,y), hypot(y,x), and hypot(x, -y) are equivalent.
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81       hypot(x, ±0) is equivalent to fabs(x).
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83       Underflow  only  happens when both x and y are subnormal and the (inex‐
84       act) result is also subnormal.
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86       These functions take precautions against overflow  during  intermediate
87       steps of the computation.
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89       On   error,   the   expressions  (math_errhandling  &  MATH_ERRNO)  and
90       (math_errhandling & MATH_ERREXCEPT) are independent of each other,  but
91       at least one of them must be non-zero.
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RATIONALE

94       None.
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FUTURE DIRECTIONS

97       None.
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SEE ALSO

100       atan2(), feclearexcept(), fetestexcept(), isnan(), sqrt()
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102       The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
103       Error Conditions for Mathematical Functions, <math.h>
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106       Portions of this text are reprinted and reproduced in  electronic  form
107       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
108       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
109       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
110       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
111       event of any discrepancy between this version and the original IEEE and
112       The Open Group Standard, the original IEEE and The Open Group  Standard
113       is  the  referee document. The original Standard can be obtained online
114       at http://www.opengroup.org/unix/online.html .
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116       Any typographical or formatting errors that appear  in  this  page  are
117       most likely to have been introduced during the conversion of the source
118       files to man page format. To report such errors,  see  https://www.ker‐
119       nel.org/doc/man-pages/reporting_bugs.html .
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123IEEE/The Open Group                  2017                            HYPOT(3P)
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