/*

**************************************************************

* C++ Mathematical Expression Toolkit Library *

* *

* Simple Example 11 *

* Author: Arash Partow (1999-2025) *

* URL: https://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. *

* https://www.opensource.org/licenses/MIT *

* SPDX-License-Identifier: MIT *

* *

**************************************************************

*/

#include <cstdio>

#include <string>

#include "exprtk.hpp"

template <typename T>

void square_wave2()

{

typedef exprtk::symbol_table<T> symbol_table_t;

typedef exprtk::expression<T> expression_t;

typedef exprtk::parser<T> parser_t;

const std::string wave_program =

" var r := 0; "

" "

" for (var i := 0; i < 1000; i += 1) "

" { "

" r += (1 / (2i + 1)) * sin((4i + 2) * pi * f * t); "

" }; "

" "

" r *= a * (4 / pi); ";

static const T pi = T(3.141592653589793238462643383279502);

T f = pi / T(10);

T t = T(0);

T a = T(10);

symbol_table_t symbol_table;

symbol_table.add_variable("f",f);

symbol_table.add_variable("t",t);

symbol_table.add_variable("a",a);

symbol_table.add_constants();

expression_t expression;

expression.register_symbol_table(symbol_table);

parser_t parser;

parser.compile(wave_program,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_wave2<double>();

return 0;

}