Re: new module 'frexp'

[Bruno Haible]

Paolo Bonzini wrote:
> I don't mind your stuff being used in the frexpl module (which would then
> be turned into LGPL).

There is no frexpl module so far. This does the first part of the change.


2007-03-22  Bruno Haible  <address@hidden>

        * lib/frexpl.c: Share code with lib/frexp.c.
        * modules/mathl (Files): Add lib/frexp.c.
        (Depends-on): Add isnanl-nolibm.

*** lib/frexpl.c        24 Feb 2007 16:31:38 -0000      1.6
--- lib/frexpl.c        22 Mar 2007 12:20:32 -0000
***************
*** 1,9 ****
! /* Emulation for frexpl.
!    Contributed by Paolo Bonzini
! 
!    Copyright 2002, 2003, 2007 Free Software Foundation, Inc.
! 
!    This file is part of gnulib.
  
     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
--- 1,5 ----
! /* Split a 'long double' into fraction and mantissa.
!    Copyright (C) 2007 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
***************
*** 19,107 ****
     with this program; if not, write to the Free Software Foundation,
     Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  
! #include <config.h>
! 
! /* Specification.  */
! #include <math.h>
! 
! #include <float.h>
! 
! /* Binary search.  Quite inefficient but portable. */
! long double
! frexpl(long double x, int *exp)
! {
!   /* Since the exponent is an 'int', it fits in 64 bits.  Therefore the
!      loops are executed no more than 64 times.  */
!   long double exponents[64];
!   long double *next;
!   int exponent, bit;
! 
!   /* Check for zero, nan and infinity. */
!   if (x != x || x + x == x)
!     {
!       *exp = 0;
!       return x;
!     }
! 
!   if (x < 0)
!     return -frexpl(-x, exp);
! 
!   exponent = 0;
!   if (x >= 1.0)
!     {
!       for (next = exponents, exponents[0] = 2.0L, bit = 1;
!          *next <= x + x;
!          bit <<= 1, next[1] = next[0] * next[0], next++);
! 
!       for (; next >= exponents; bit >>= 1, next--)
!       if (x + x >= *next)
!         {
!           x /= *next;
!           exponent |= bit;
!         }
! 
!     }
! 
!   else if (x < 0.5)
!     {
!       for (next = exponents, exponents[0] = 0.5L, bit = 1;
!          *next > x;
!          bit <<= 1, next[1] = next[0] * next[0], next++);
! 
!       for (; next >= exponents; bit >>= 1, next--)
!       if (x < *next)
!         {
!           x /= *next;
!           exponent |= bit;
!         }
! 
!       exponent = -exponent;
!     }
! 
!   *exp = exponent;
!   return x;
! }
! 
! #if 0
! int
! main (void)
! {
!   long double x;
!   int y;
!   x = frexpl(0.0L / 0.0L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(1.0L / 0.0L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(-1.0L / 0.0L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.5L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.75L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(1.0L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(3.6L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(17.8L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(8.0L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.3L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.49L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.049L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.0245L, &y); printf ("%.6Lg %d\n", x, y);
!   x = frexpl(0.0625L, &y); printf ("%.6Lg %d\n", x, y);
! }
! #endif
! 
--- 15,19 ----
     with this program; if not, write to the Free Software Foundation,
     Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  
! #define USE_LONG_DOUBLE
! #include "frexp.c"
*** modules/mathl       18 Feb 2007 15:10:28 -0000      1.5
--- modules/mathl       22 Mar 2007 12:20:32 -0000
***************
*** 10,15 ****
--- 10,16 ----
  lib/expl.c
  lib/floorl.c
  lib/frexpl.c
+ lib/frexp.c
  lib/ldexpl.c
  lib/logl.c
  lib/sincosl.c
***************
*** 22,27 ****
--- 23,29 ----
  
  Depends-on:
  math
+ isnanl-nolibm
  
  configure.ac:
  gl_FUNC_LONG_DOUBLE_MATH