exprtk/exprtk_simple_example_17.cpp at master · losttem/exprtk · GitHub

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

* C++ Mathematical Expression Toolkit Library *

* *

* Simple Example 17 *

* Author: Arash Partow (1999-2022) *

* 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 <cstdlib>

#include <ctime>

#include <string>

#include "exprtk.hpp"

template <typename T>

struct rnd_01 : public exprtk::ifunction<T>

{

using exprtk::ifunction<T>::operator();

rnd_01() : exprtk::ifunction<T>(0)

{ ::srand(static_cast<unsigned int>(time(NULL))); }

inline T operator()()

{

// Note: Do not use this in production

// Result is in the interval [0,1)

return T(::rand() / T(RAND_MAX + 1.0));

}

};

template <typename T>

void monte_carlo_pi()

{

typedef exprtk::symbol_table<T> symbol_table_t;

typedef exprtk::expression<T> expression_t;

typedef exprtk::parser<T> parser_t;

const std::string monte_carlo_pi_program =

" var experiments[5 * 10^7] := [(rnd_01^2 + rnd_01^2) <= 1]; "

" 4 * sum(experiments) / experiments[]; ";

rnd_01<T> rnd01;

symbol_table_t symbol_table;

symbol_table.add_function("rnd_01",rnd01);

expression_t expression;

expression.register_symbol_table(symbol_table);

parser_t parser;

parser.compile(monte_carlo_pi_program,expression);

const T approximate_pi = expression.value();

const T real_pi = T(3.141592653589793238462643383279502); // or close enough...

printf("pi ~ %20.17f\terror: %20.17f\n",

approximate_pi,

std::abs(real_pi - approximate_pi));

}

int main()

{

monte_carlo_pi<double>();

return 0;

}

exprtk/exprtk_simple_example_17.cpp at master · losttem/exprtk · GitHub

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