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/*
**************************************************************
* C++ Mathematical Expression Toolkit Library *
* *
* Simple Example 04 *
* Author: Arash Partow (1999-2024) *
* 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 fibonacci()
{
typedef exprtk::symbol_table<T> symbol_table_t;
typedef exprtk::expression<T> expression_t;
typedef exprtk::parser<T> parser_t;
typedef exprtk::function_compositor<T> compositor_t;
typedef typename compositor_t::function function_t;
T x = T(0);
compositor_t compositor;
compositor.add(
function_t("fibonacci")
.var("x")
.expression
(
" switch "
" { "
" case x == 0 : 0; "
" case x == 1 : 1; "
" default : "
" { "
" var prev := 0; "
" var curr := 1; "
" while ((x -= 1) > 0) "
" { "
" var temp := prev; "
" prev := curr; "
" curr += temp; "
" }; "
" }; "
" } "
));
symbol_table_t& symbol_table = compositor.symbol_table();
symbol_table.add_constants();
symbol_table.add_variable("x",x);
std::string expression_str = "fibonacci(x)";
expression_t expression;
expression.register_symbol_table(symbol_table);
parser_t parser;
parser.compile(expression_str,expression);
for (std::size_t i = 0; i < 40; ++i)
{
x = static_cast<T>(i);
const T result = expression.value();
printf("fibonacci(%3d) = %10.0f\n",
static_cast<int>(i),
result);
}
}
int main()
{
fibonacci<double>();
return 0;
}
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