version 1.1, 2000/01/10 15:35:22 |
version 1.1.1.3, 2003/08/25 16:06:35 |
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/* mpf_set_prec(x) -- Change the precision of x. |
/* mpf_set_prec(x) -- Change the precision of x. |
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Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc. |
Copyright 1993, 1994, 1995, 2000, 2001 Free Software Foundation, Inc. |
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This file is part of the GNU MP Library. |
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 |
The GNU MP Library is free software; you can redistribute it and/or modify |
it under the terms of the GNU Library General Public License as published by |
it under the terms of the GNU Lesser General Public License as published by |
the Free Software Foundation; either version 2 of the License, or (at your |
the Free Software Foundation; either version 2.1 of the License, or (at your |
option) any later version. |
option) any later version. |
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The GNU MP Library is distributed in the hope that it will be useful, but |
The GNU MP Library is distributed in the hope that it will be useful, but |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
License for more details. |
License for more details. |
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You should have received a copy of the GNU Library General Public License |
You should have received a copy of the GNU Lesser General Public License |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
MA 02111-1307, USA. */ |
MA 02111-1307, USA. */ |
Line 22 MA 02111-1307, USA. */ |
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Line 22 MA 02111-1307, USA. */ |
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#include "gmp.h" |
#include "gmp.h" |
#include "gmp-impl.h" |
#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 |
void |
#if __STDC__ |
mpf_set_prec (mpf_ptr x, unsigned long int new_prec_in_bits) |
mpf_set_prec (mpf_ptr x, unsigned long int prec_in_bits) |
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#else |
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mpf_set_prec (x, prec_in_bits) |
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mpf_ptr x; |
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unsigned long int prec_in_bits; |
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#endif |
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{ |
{ |
mp_size_t prec; |
mp_size_t old_prec, new_prec, new_prec_plus1; |
mp_size_t size = ABS (x->_mp_size); |
mp_size_t size, sign; |
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mp_ptr xp; |
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prec = (MAX (53, prec_in_bits) + 2 * BITS_PER_MP_LIMB - 1)/BITS_PER_MP_LIMB; |
new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits); |
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old_prec = PREC(x); |
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/* We want the most significant limbs, so move the limbs down if we are |
/* do nothing if already the right precision */ |
about to truncate the value. */ |
if (new_prec == old_prec) |
if (size > prec + 1) |
return; |
{ |
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mp_size_t offset = size - (prec + 1); |
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mp_ptr xp = x->_mp_d; |
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MPN_COPY (xp, xp + offset, prec + 1); |
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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x->_mp_d = (mp_ptr) (*_mp_reallocate_func) |
PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1); |
(x->_mp_d, |
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(x->_mp_prec + 1) * BYTES_PER_MP_LIMB, (prec + 1) * BYTES_PER_MP_LIMB); |
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x->_mp_prec = prec; |
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/* If the precision decreased, truncate the number. */ |
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if (size > prec + 1) |
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x->_mp_size = x->_mp_size >= 0 ? (prec + 1) : -(prec + 1); |
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} |
} |