efee5258bc
The MPFR library is a C library for multiple-precision floating-point computations with exact rounding (also called correct rounding). It is based on the GMP multiple-precision library and should replace the MPF class in further releases of GMP. GCC >= 4.2 requires MPFR.
87 lines
2.6 KiB
C
87 lines
2.6 KiB
C
/* mpfr_fits_*_p -- test whether an mpfr fits a C signed type.
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Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao projects, INRIA.
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Copied from mpf/fits_s.h.
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This file is part of the GNU MPFR Library.
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The GNU MPFR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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The GNU MPFR Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
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http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
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51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
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#include "mpfr-impl.h"
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int
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FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
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{
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mpfr_exp_t e;
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int prec;
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mpfr_t x;
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int neg;
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int res;
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if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
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/* Zero always fit */
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return MPFR_IS_ZERO (f) ? 1 : 0;
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/* now it fits if either
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(a) MINIMUM <= f <= MAXIMUM
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(b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */
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e = MPFR_GET_EXP (f);
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if (e < 1)
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return 1; /* |f| < 1: always fits */
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neg = MPFR_IS_NEG (f);
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/* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */
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/* first compute prec(EXTREMUM), this could be done at configure time,
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but the result can depend on neg (the loop is moved inside the "if"
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to give the compiler a better chance to compute prec statically) */
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if (neg)
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{
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unsigned TYPE s;
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/* In C89, the division on negative integers isn't well-defined. */
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s = SAFE_ABS (unsigned TYPE, MINIMUM);
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for (prec = 0; s != 0; s /= 2, prec ++);
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}
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else
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{
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TYPE s;
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s = MAXIMUM;
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for (prec = 0; s != 0; s /= 2, prec ++);
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}
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/* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */
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/* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */
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if (e <= prec - 1)
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return 1;
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/* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */
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if (e >= prec + 1)
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return 0;
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MPFR_ASSERTD (e == prec);
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/* hard case: first round to prec bits, then check */
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mpfr_init2 (x, prec);
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mpfr_set (x, f, rnd);
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res = neg ? (mpfr_cmp_si (x, MINIMUM) >= 0) : (MPFR_GET_EXP (x) == e);
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mpfr_clear (x);
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return res;
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}
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