55 lines
2.2 KiB
C
55 lines
2.2 KiB
C
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/*
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* nut_float.h - Network UPS Tools include files for floating point routines
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* and ways to compare if non-integers are close enough to assume equal
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*
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* Copyright (C) 2020 Jim Klimov <jimklimov@gmail.com>
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*
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* This program 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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*
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* This program 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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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef NUT_FLOAT_H_SEEN
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#define NUT_FLOAT_H_SEEN 1
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#include "config.h"
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#if defined HAVE_FLOAT_H
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# include <float.h>
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#endif
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#if defined HAVE_MATH_H
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# include <math.h>
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#endif
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/* Modern compilers frown upon direct comparisons of floating point numbers
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* since their imprecise internal representations can misfire, and really we
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* care if they are indiscernably close. To aviod warnings like -Wfloat-equal
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* we prefer to compare with methods defined below. Note: despite the "floating"
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* name, fabs() seems to be defined over doubles or wider types, e.g.:
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* double fabs(double x);
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* float fabsf(float x);
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* long double fabsl(long double x);
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* To be on the safer side, we compare the difference to be smaller or equal to
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* the Epsilon for the respective numeric type, in order to be equivalent to a
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* zero for our needs. Various libs define it as "the next representable number
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* after 1.0 which is not equal to 1.0" for the discrete maths involved; no talk
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* about exactly comparing it to zero or whether it is the smallest representable
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* non-zero value...
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*/
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#define f_equal(x, y) ( fabsf((float)(x) - (float)(y)) <= FLT_EPSILON )
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#define d_equal(x, y) ( fabs((double)(x) - (double)(y)) <= DBL_EPSILON )
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#define ld_equal(x, y) ( fabsl((long double)(x) - (long double)(y)) <= LDBL_EPSILON )
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#endif /* NUT_FLOAT_H_SEEN */
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