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exprtk_simple_example_02.cpp
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exprtk_simple_example_02.cpp
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/*
**************************************************************
* C++ Mathematical Expression Toolkit Library *
* *
* Simple Example 2 *
* Author: Arash Partow (1999-2019) *
* URL: http://www.partow.net/programming/exprtk/index.html *
* *
* Copyright notice: *
* Free use of the Mathematical Expression Toolkit Library is *
* permitted under the guidelines and in accordance with the *
* most current version of the MIT License. *
* http://www.opensource.org/licenses/MIT *
* *
**************************************************************
*/
#include <cstdio>
#include <string>
#include "exprtk.hpp"
template <typename T>
void square_wave()
{
typedef exprtk::symbol_table<T> symbol_table_t;
typedef exprtk::expression<T> expression_t;
typedef exprtk::parser<T> parser_t;
const std::string expr_string =
"a*(4/pi)*"
"((1 /1)*sin( 2*pi*f*t)+(1 /3)*sin( 6*pi*f*t)+"
" (1 /5)*sin(10*pi*f*t)+(1 /7)*sin(14*pi*f*t)+"
" (1 /9)*sin(18*pi*f*t)+(1/11)*sin(22*pi*f*t)+"
" (1/13)*sin(26*pi*f*t)+(1/15)*sin(30*pi*f*t)+"
" (1/17)*sin(34*pi*f*t)+(1/19)*sin(38*pi*f*t)+"
" (1/21)*sin(42*pi*f*t)+(1/23)*sin(46*pi*f*t)+"
" (1/25)*sin(50*pi*f*t)+(1/27)*sin(54*pi*f*t))";
static const T pi = T(3.141592653589793238462643383279502);
const T f = pi / T(10);
const T a = T(10);
T t = T(0);
symbol_table_t symbol_table;
symbol_table.add_variable("t",t);
symbol_table.add_constant("f",f);
symbol_table.add_constant("a",a);
symbol_table.add_constants();
expression_t expression;
expression.register_symbol_table(symbol_table);
parser_t parser;
parser.compile(expr_string,expression);
const T delta = (T(4) * pi) / T(1000);
for (t = (T(-2) * pi); t <= (T(+2) * pi); t += delta)
{
const T result = expression.value();
printf("%19.15f\t%19.15f\n", t, result);
}
}
int main()
{
square_wave<double>();
return 0;
}