60 lines
1.9 KiB
C
60 lines
1.9 KiB
C
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/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2009 William Hart
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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#include "fmpz.h"
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void
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fmpz_submul(fmpz_t f, const fmpz_t g, const fmpz_t h)
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{
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fmpz c1 = *g;
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if (!COEFF_IS_MPZ(c1)) /* g is small */
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{
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if (c1 < WORD(0))
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fmpz_addmul_ui(f, h, -c1);
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else
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fmpz_submul_ui(f, h, c1);
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}
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else
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{
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fmpz c2 = *h;
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if (!COEFF_IS_MPZ(c2)) /* h is small */
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{
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if (c2 < WORD(0))
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fmpz_addmul_ui(f, g, -c2);
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else
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fmpz_submul_ui(f, g, c2);
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}
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else /* both g and h are large */
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{
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__mpz_struct *mpz_ptr = _fmpz_promote_val(f);
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mpz_submul(mpz_ptr, COEFF_TO_PTR(c1), COEFF_TO_PTR(c2));
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_fmpz_demote_val(f); /* cancellation may have occurred */
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}
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}
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}
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