66 lines
2.1 KiB
C
66 lines
2.1 KiB
C
/* Example illustrating how to use mpfr_can_round. */
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/*
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Copyright 2016-2022 Free Software Foundation, Inc.
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Contributed by the AriC and Caramba projects, INRIA.
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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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https://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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*/
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#include <stdio.h>
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#include <mpfr.h>
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int
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main (void)
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{
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mpfr_t x, y;
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mpfr_prec_t px = 53, py = 50;
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mpfr_rnd_t r1, r2;
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int ok;
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/* Given an approximation of Pi to px bits computed with rounding mode r1,
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we call mpfr_can_round() to see if we can deduced the correct rounding
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of Pi to py bits with rounding mode r2.
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The error is at most 1 = 2^0 ulp. This translates into err = prec(x). */
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mpfr_init2 (x, px);
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mpfr_init2 (y, py);
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for (r1 = 0; r1 < 4; r1++)
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{
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mpfr_const_pi (x, r1);
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printf ("r1=%s approx=", mpfr_print_rnd_mode (r1));
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mpfr_out_str (stdout, 2, 0, x, MPFR_RNDN);
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printf ("\n");
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for (r2 = 0; r2 < 4; r2++)
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{
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ok = mpfr_can_round (x, mpfr_get_prec (x), r1, r2, py);
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printf ("r2=%s ok=%d", mpfr_print_rnd_mode (r2), ok);
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if (ok)
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{
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mpfr_set (y, x, r2);
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printf (" ");
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mpfr_out_str (stdout, 2, 0, y, MPFR_RNDN);
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}
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printf ("\n");
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}
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}
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mpfr_clear (x);
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mpfr_clear (y);
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mpfr_free_cache ();
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return 0;
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}
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