91 lines
2.7 KiB
C++
91 lines
2.7 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 04 *
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* Author: Arash Partow (1999-2024) *
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* URL: https://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 MIT License. *
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* https://www.opensource.org/licenses/MIT *
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* SPDX-License-Identifier: MIT *
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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 fibonacci()
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{
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typedef exprtk::symbol_table<T> symbol_table_t;
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typedef exprtk::expression<T> expression_t;
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typedef exprtk::parser<T> parser_t;
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typedef exprtk::function_compositor<T> compositor_t;
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typedef typename compositor_t::function function_t;
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T x = T(0);
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compositor_t compositor;
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compositor.add(
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function_t("fibonacci")
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.var("x")
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.expression
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(
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" switch "
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" { "
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" case x == 0 : 0; "
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" case x == 1 : 1; "
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" default : "
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" { "
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" var prev := 0; "
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" var curr := 1; "
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" while ((x -= 1) > 0) "
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" { "
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" var temp := prev; "
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" prev := curr; "
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" curr += temp; "
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" }; "
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" }; "
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" } "
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));
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symbol_table_t& symbol_table = compositor.symbol_table();
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symbol_table.add_constants();
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symbol_table.add_variable("x",x);
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std::string expression_str = "fibonacci(x)";
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expression_t expression;
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expression.register_symbol_table(symbol_table);
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parser_t parser;
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parser.compile(expression_str,expression);
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for (std::size_t i = 0; i < 40; ++i)
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{
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x = static_cast<T>(i);
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const T result = expression.value();
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printf("fibonacci(%3d) = %10.0f\n",
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static_cast<int>(i),
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result);
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}
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}
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int main()
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{
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fibonacci<double>();
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return 0;
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}
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