61 lines
2.0 KiB
C
61 lines
2.0 KiB
C
/* mpf_set_prec(x) -- Change the precision of x.
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Copyright 1993, 1994, 1995, 2000, 2001 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP 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 2.1 of the License, or (at your
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option) any later version.
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The GNU MP 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 MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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/* A full new_prec+1 limbs are always retained, even though just new_prec
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would satisfy the requested precision. If size==new_prec+1 then
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certainly new_prec+1 should be kept since no copying is needed in that
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case. If just new_prec was kept for size>new_prec+1 it'd be a bit
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inconsistent. */
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void
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mpf_set_prec (mpf_ptr x, unsigned long int new_prec_in_bits)
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{
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mp_size_t old_prec, new_prec, new_prec_plus1;
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mp_size_t size, sign;
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mp_ptr xp;
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new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits);
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old_prec = PREC(x);
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/* do nothing if already the right precision */
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if (new_prec == old_prec)
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return;
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PREC(x) = new_prec;
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new_prec_plus1 = new_prec + 1;
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/* retain most significant limbs */
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sign = SIZ(x);
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size = ABS (sign);
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xp = PTR(x);
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if (size > new_prec_plus1)
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{
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SIZ(x) = (sign >= 0 ? new_prec_plus1 : -new_prec_plus1);
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MPN_COPY_INCR (xp, xp + size - new_prec_plus1, new_prec_plus1);
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}
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PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1);
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}
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