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author | Ludovic Courtès <ludo@gnu.org> | 2011-02-14 11:36:25 +0100 |
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committer | Ludovic Courtès <ludo@gnu.org> | 2011-02-14 11:36:25 +0100 |
commit | 49114fd43de833c0724fbb0b6dc9ca639d1ab74f (patch) | |
tree | bd33e1612cbbc37218ff18a229ff603018d2d5d5 /lib/trunc.c | |
parent | d9a00aa53612b97b11847cfc03647a3ab54b2a48 (diff) | |
download | guile-49114fd43de833c0724fbb0b6dc9ca639d1ab74f.tar.gz |
Update Gnulib; add new modules.
This updates Gnulib to v0.0-4889-ge375fe3.
* m4/gnulib-cache.m4: Add `accept', `bind', `close', `connect',
`getpeername', `getsockname', `getsockopt', `listen', `malloc',
`malloca', `recv', `recvfrom', `send', `sendto', `setsockopt',
`shutdown', `socket', and `sockets', requested by
Jan Nieuwenhuizen <janneke-list@xs4all.nl> for cross-MinGW32 builds.
Add `trunc', requested by Mark H Weaver <mhw@netris.org>.
Diffstat (limited to 'lib/trunc.c')
-rw-r--r-- | lib/trunc.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/lib/trunc.c b/lib/trunc.c new file mode 100644 index 000000000..f213b26b5 --- /dev/null +++ b/lib/trunc.c @@ -0,0 +1,113 @@ +/* Round towards zero. + Copyright (C) 2007, 2010-2011 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser 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 Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +/* Written by Bruno Haible <bruno@clisp.org>, 2007. */ + +#include <config.h> + +/* Specification. */ +#include <math.h> + +#include <float.h> + +#undef MIN + +#ifdef USE_LONG_DOUBLE +# define FUNC truncl +# define DOUBLE long double +# define MANT_DIG LDBL_MANT_DIG +# define MIN LDBL_MIN +# define L_(literal) literal##L +#elif ! defined USE_FLOAT +# define FUNC trunc +# define DOUBLE double +# define MANT_DIG DBL_MANT_DIG +# define MIN DBL_MIN +# define L_(literal) literal +#else /* defined USE_FLOAT */ +# define FUNC truncf +# define DOUBLE float +# define MANT_DIG FLT_MANT_DIG +# define MIN FLT_MIN +# define L_(literal) literal##f +#endif + +/* -0.0. See minus-zero.h. */ +#if defined __hpux || defined __sgi || defined __ICC +# define MINUS_ZERO (-MIN * MIN) +#else +# define MINUS_ZERO L_(-0.0) +#endif + +/* 2^(MANT_DIG-1). */ +static const DOUBLE TWO_MANT_DIG = + /* Assume MANT_DIG <= 5 * 31. + Use the identity + n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */ + (DOUBLE) (1U << ((MANT_DIG - 1) / 5)) + * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5)) + * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5)) + * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5)) + * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5)); + +DOUBLE +FUNC (DOUBLE x) +{ + /* The use of 'volatile' guarantees that excess precision bits are dropped + at each addition step and before the following comparison at the caller's + site. It is necessary on x86 systems where double-floats are not IEEE + compliant by default, to avoid that the results become platform and compiler + option dependent. 'volatile' is a portable alternative to gcc's + -ffloat-store option. */ + volatile DOUBLE y = x; + volatile DOUBLE z = y; + + if (z > L_(0.0)) + { + /* For 0 < x < 1, return +0.0 even if the current rounding mode is + FE_DOWNWARD. */ + if (z < L_(1.0)) + z = L_(0.0); + /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1. */ + else if (z < TWO_MANT_DIG) + { + /* Round to the next integer (nearest or up or down, doesn't matter). */ + z += TWO_MANT_DIG; + z -= TWO_MANT_DIG; + /* Enforce rounding down. */ + if (z > y) + z -= L_(1.0); + } + } + else if (z < L_(0.0)) + { + /* For -1 < x < 0, return -0.0 regardless of the current rounding + mode. */ + if (z > L_(-1.0)) + z = MINUS_ZERO; + /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */ + else if (z > - TWO_MANT_DIG) + { + /* Round to the next integer (nearest or up or down, doesn't matter). */ + z -= TWO_MANT_DIG; + z += TWO_MANT_DIG; + /* Enforce rounding up. */ + if (z < y) + z += L_(1.0); + } + } + return z; +} |