kc3-lang/gnulib/lib/hypot.c

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• Hash : 9fb732a4
  Author :
  Date : 2012-02-29T20:00:38
  

  hypot-ieee: Work around test failure on OSF/1 and native Windows.
  
  * lib/math.in.h (hypot): New declaration.
  * lib/hypot.c: New file.
  * m4/hypot-ieee.m4: New file.
  * m4/hypot.m4 (gl_FUNC_HYPOT): If gl_FUNC_HYPOT_IEEE is present, test
  whether hypot works with mixed NaN and Infinity arguments. Replace it
  if not.
  * m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize GNULIB_HYPOT,
  REPLACE_HYPOT.
  * modules/math (Makefile.am): Substitute GNULIB_HYPOT, REPLACE_HYPOT.
  * modules/hypot (Files): Add lib/hypot.c.
  (Depends-on): Add dependencies.
  (configure.ac): Arrange to compile replacement if REPLACE_HYPOT is 1.
  * modules/hypot-ieee (Files): Add m4/hypot-ieee.m4.
  (configure.ac): Invoke gl_FUNC_HYPOT_IEEE.
  * tests/test-math-c++.cc: Check the declaration of hypot.
  * doc/posix-functions/hypot.texi: Mention the hypot-ieee module.
  

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• lib/hypot.c

• /* Hypotenuse of a right-angled triangle.
     Copyright (C) 2012 Free Software Foundation, Inc.
  
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  /* Written by Bruno Haible <bruno@clisp.org>, 2012.  */
  
  #include <config.h>
  
  /* Specification.  */
  #include <math.h>
  
  double
  hypot (double x, double y)
  {
    if (isfinite (x) && isfinite (y))
      {
        /* Determine absolute values.  */
        x = fabs (x);
        y = fabs (y);
  
        {
          /* Find the bigger and the smaller one.  */
          double a;
          double b;
  
          if (x >= y)
            {
              a = x;
              b = y;
            }
          else
            {
              a = y;
              b = x;
            }
          /* Now 0 <= b <= a.  */
  
          {
            int e;
            double an;
            double bn;
  
            /* Write a = an * 2^e, b = bn * 2^e with 0 <= bn <= an < 1.  */
            an = frexp (a, &e);
            bn = ldexp (b, - e);
  
            {
              double cn;
  
              /* Through the normalization, no unneeded overflow or underflow
                 will occur here.  */
              cn = sqrt (an * an + bn * bn);
              return ldexp (cn, e);
            }
          }
        }
      }
    else
      {
        if (isinf (x) || isinf (y))
          /* x or y is infinite.  Return +Infinity.  */
          return HUGE_VAL;
        else
          /* x or y is NaN.  Return NaN.  */
          return x + y;
      }
  }
  

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