65 lines
2.2 KiB
C++
65 lines
2.2 KiB
C++
/*
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**************************************************************
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* C++ Mathematical Expression Toolkit Library *
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* *
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* Simple Example 2 *
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* Author: Arash Partow (1999-2014) *
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* URL: http://www.partow.net/programming/exprtk/index.html *
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* *
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* Copyright notice: *
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* Free use of the Mathematical Expression Toolkit Library is *
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* permitted under the guidelines and in accordance with the *
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* most current version of the Common Public License. *
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* http://www.opensource.org/licenses/cpl1.0.php *
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* *
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**************************************************************
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*/
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#include <cstdio>
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#include <string>
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#include "exprtk.hpp"
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template<typename T>
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void square_wave()
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{
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std::string expr_string = "a*(4/pi)*"
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"((1 /1)*sin( 2*pi*f*t)+(1 /3)*sin( 6*pi*f*t)+"
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" (1 /5)*sin(10*pi*f*t)+(1 /7)*sin(14*pi*f*t)+"
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" (1 /9)*sin(18*pi*f*t)+(1/11)*sin(22*pi*f*t)+"
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" (1/13)*sin(26*pi*f*t)+(1/15)*sin(30*pi*f*t)+"
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" (1/17)*sin(34*pi*f*t)+(1/19)*sin(38*pi*f*t)+"
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" (1/21)*sin(42*pi*f*t)+(1/23)*sin(46*pi*f*t)+"
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" (1/25)*sin(50*pi*f*t)+(1/27)*sin(54*pi*f*t))";
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static const T pi = T(3.14159265358979323846);
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T f = pi / T(10);
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T t = T(0);
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T a = T(10);
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exprtk::symbol_table<T> symbol_table;
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symbol_table.add_variable("f",f);
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symbol_table.add_variable("t",t);
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symbol_table.add_variable("a",a);
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symbol_table.add_constants();
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exprtk::expression<T> expression;
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expression.register_symbol_table(symbol_table);
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exprtk::parser<T> parser;
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parser.compile(expr_string,expression);
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const T delta = (T(4) * pi) / T(1000);
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for (t = (T(-2) * pi); t <= (T(+2) * pi); t += delta)
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{
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T result = expression.value();
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printf("%19.15f\t%19.15f\n",t,result);
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}
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}
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int main()
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{
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square_wave<double>();
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return 0;
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}
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