mirror of
https://github.com/jkriege2/JKQtPlotter.git
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64 lines
2.1 KiB
C++
64 lines
2.1 KiB
C++
/*
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Copyright (c) 2008-2024 Jan W. Krieger (<jan@jkrieger.de>)
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This software 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 (LGPL) as published by
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the Free Software Foundation, either version 2.1 of the License, or
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(at your option) any later version.
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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 Lesser General Public License (LGPL) for more details.
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You should have received a copy of the GNU Lesser General Public License (LGPL)
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "jkqtcommon/jkqtpmathtools.h"
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#include <cmath>
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uint64_t jkqtp_gcd(uint64_t a, uint64_t b)
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{
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if (a == 0)
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return b;
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else if (b == 0)
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return a;
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if (a < b)
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return jkqtp_gcd(a, b % a);
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else
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return jkqtp_gcd(b, a % b);
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}
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void jkqtp_estimateFraction(double input, int& sign, uint64_t &intpart, uint64_t &num, uint64_t &denom, unsigned int precision)
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{
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// see https://stackoverflow.com/a/28662740
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// https://stackoverflow.com/questions/4819075/how-to-output-fraction-instead-of-decimal-number
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// https://stackoverflow.com/a/64828741
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// https://stackoverflow.com/questions/26643695/converting-a-floating-point-decimal-value-to-a-fraction
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sign=+1;
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if (input<0.0) {
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sign=-1;
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input=fabs(input);
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}
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// now input is guaranteed positive and sign stores the sign +1 or -1
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const double integral = std::floor(input);
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const double frac = input - integral;
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const double prec = pow(10,precision); // This is the accuracy.
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uint64_t gcd_ = jkqtp_gcd(static_cast<uint64_t>(round(frac * prec)), static_cast<uint64_t>(prec));
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denom = static_cast<uint64_t>(prec / gcd_);
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num = static_cast<uint64_t>(round(frac * prec) / gcd_);
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intpart=static_cast<uint64_t>(integral);
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}
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