/* Example illustrating how to use mpfr_can_round. */ /* Copyright 2016-2018 Free Software Foundation, Inc. Contributed by the AriC and Caramba projects, INRIA. This file is part of the GNU MPFR Library. The GNU MPFR Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. The GNU MPFR Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ #include <stdio.h> #include <mpfr.h> int main (void) { mpfr_t x, y; mpfr_prec_t px = 53, py = 50; mpfr_rnd_t r1, r2; int ok; /* Given an approximation of Pi to px bits computed with rounding mode r1, we call mpfr_can_round() to see if we can deduced the correct rounding of Pi to py bits with rounding mode r2. The error is at most 1 = 2^0 ulp. This translates into err = prec(x). */ mpfr_init2 (x, px); mpfr_init2 (y, py); for (r1 = 0; r1 < 4; r1++) { mpfr_const_pi (x, r1); printf ("r1=%s approx=", mpfr_print_rnd_mode (r1)); mpfr_out_str (stdout, 2, 0, x, MPFR_RNDN); printf ("\n"); for (r2 = 0; r2 < 4; r2++) { ok = mpfr_can_round (x, mpfr_get_prec (x), r1, r2, py); printf ("r2=%s ok=%d", mpfr_print_rnd_mode (r2), ok); if (ok) { mpfr_set (y, x, r2); printf (" "); mpfr_out_str (stdout, 2, 0, y, MPFR_RNDN); } printf ("\n"); } } mpfr_clear (x); mpfr_clear (y); return 0; } |