man3/hypot.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  30 .\" Modified 2002-07-27 by Walter Harms
  31 .\"     (walter.harms@informatik.uni-oldenburg.de)
  32 .\"
  33 .TH HYPOT 3 2016-03-15 ""  "Linux Programmer's Manual"
  34 .SH NAME
  35 hypot, hypotf, hypotl \- Euclidean distance function
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <math.h>
  39 .PP
  40 .BI "double hypot(double " x ", double " y );
  41 .br
  42 .BI "float hypotf(float " x ", float " y );
  43 .br
  44 .BI "long double hypotl(long double " x ", long double " y );
  45 .fi
  46 .PP
  47 Link with \fI\-lm\fP.
  48 .PP
  49 .in -4n
  50 Feature Test Macro Requirements for glibc (see
  51 .BR feature_test_macros (7)):
  52 .in
  53 .PP
  54 .ad l
  55 .BR hypot ():
  56 .RS 4
  57 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  58     || _XOPEN_SOURCE
  59     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  60     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  61 .RE
  62 .br
  63 .BR hypotf (),
  64 .BR hypotl ():
  65 .RS 4
  66 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  67     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  68     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  69 .RE
  70 .ad b
  71 .SH DESCRIPTION
  72 These functions return
  73 .RI sqrt( x * x + y * y ).
  74 This is the length of the hypotenuse of a right-angled triangle
  75 with sides of length
  76 .I x
  77 and
  78 .IR y ,
  79 or the distance of the point
  80 .RI ( x , y )
  81 from the origin.
  82 .PP
  83 The calculation is performed without undue overflow or underflow
  84 during the intermediate steps of the calculation.
  85 .\" e.g., hypot(DBL_MIN, DBL_MIN) does the right thing, as does, say
  86 .\" hypot(DBL_MAX/2.0, DBL_MAX/2.0).
  87 .SH RETURN VALUE
  88 On success, these functions return the length of a right-angled triangle
  89 with sides of length
  90 .I x
  91 and
  92 .IR y .
  93 .PP
  94 If
  95 .I x
  96 or
  97 .I y
  98 is an infinity,
  99 positive infinity is returned.
 100 .PP
 101 If
 102 .I x
 103 or
 104 .I y
 105 is a NaN,
 106 and the other argument is not an infinity,
 107 a NaN is returned.
 108 .PP
 109 If the result overflows,
 110 a range error occurs,
 111 and the functions return
 112 .BR HUGE_VAL ,
 113 .BR HUGE_VALF ,
 114 or
 115 .BR HUGE_VALL ,
 116 respectively.
 117 .PP
 118 If both arguments are subnormal, and the result is subnormal,
 119 .\" Actually, could the result not be subnormal if both arguments
 120 .\" are subnormal?  I think not -- mtk, Jul 2008
 121 a range error occurs,
 122 and the correct result is returned.
 123 .SH ERRORS
 124 See
 125 .BR math_error (7)
 126 for information on how to determine whether an error has occurred
 127 when calling these functions.
 128 .PP
 129 The following errors can occur:
 130 .TP
 131 Range error: result overflow
 132 .I errno
 133 is set to
 134 .BR ERANGE .
 135 An overflow floating-point exception
 136 .RB ( FE_OVERFLOW )
 137 is raised.
 138 .TP
 139 Range error: result underflow
 140 .\" .I errno
 141 .\" is set to
 142 .\" .BR ERANGE .
 143 An underflow floating-point exception
 144 .RB ( FE_UNDERFLOW )
 145 is raised.
 146 .IP
 147 These functions do not set
 148 .IR errno
 149 for this case.
 150 .\" FIXME . Is it intentional that these functions do not set errno?
 151 .\" They do set errno for the overflow case.
 152 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6795
 153 .SH ATTRIBUTES
 154 For an explanation of the terms used in this section, see
 155 .BR attributes (7).
 156 .TS
 157 allbox;
 158 lbw27 lb lb
 159 l l l.
 160 Interface       Attribute       Value
 161 T{
 162 .BR hypot (),
 163 .BR hypotf (),
 164 .BR hypotl ()
 165 T}      Thread safety   MT-Safe
 166 .TE
 167 .sp 1
 168 .SH CONFORMING TO
 169 C99, POSIX.1-2001, POSIX.1-2008.
 170 .PP
 171 The variant returning
 172 .I double
 173 also conforms to
 174 SVr4, 4.3BSD.
 175 .SH SEE ALSO
 176 .BR cabs (3),
 177 .BR sqrt (3)