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/*
**************************************************************
* C++ Mathematical Expression Toolkit Library *
* *
* Simple Example 24 *
* 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, T Process(const unsigned char)>
struct char_process : public exprtk::igeneric_function<T>
{
typedef typename exprtk::igeneric_function<T> igfun_t;
typedef typename igfun_t::parameter_list_t parameter_list_t;
typedef typename igfun_t::generic_type generic_type;
typedef typename generic_type::string_view string_t;
using exprtk::igeneric_function<T>::operator();
char_process()
: exprtk::igeneric_function<T>("S")
{}
inline T operator()(parameter_list_t parameters)
{
const unsigned char c = string_t(parameters[0])[0];
return Process(c);
}
};
template <typename T>
T is_digit_func(const unsigned char c)
{
return (('0' <= c) && (c <= '9')) ? T(1) : T(0);
}
template <typename T>
T to_num_func(const unsigned char c)
{
return static_cast<T>(c - '0');
}
template <typename T>
void rpn_example()
{
typedef exprtk::symbol_table<T> symbol_table_t;
typedef exprtk::expression<T> expression_t;
typedef exprtk::parser<T> parser_t;
const std::string rpn_program =
" var stack[1000] := [0]; "
" var stack_size := 0; "
" "
" for (var i := 0; i < rpn_expression[]; i += 1) "
" { "
" var c := rpn_expression[i : i + 1]; "
" "
" if (c == ' ') "
" { "
" continue; "
" } "
" else if (is_digit(c)) "
" { "
" stack[stack_size] := to_num(c); "
" stack_size += 1; "
" } "
" else "
" { "
" var operator := c; "
" var operand1 := stack[stack_size - 2]; "
" var operand2 := stack[stack_size - 1]; "
" stack_size -= 2; "
" "
" switch "
" { "
" case operator == '+' : stack[stack_size] := operand1 + operand2; "
" case operator == '-' : stack[stack_size] := operand1 - operand2; "
" case operator == '*' : stack[stack_size] := operand1 * operand2; "
" case operator == '/' : stack[stack_size] := operand1 / operand2; "
" case operator == '^' : stack[stack_size] := operand1 ^ operand2; "
" }; "
" "
" stack_size += 1; "
" } "
" }; "
" "
" println(stack[0], ' = ', rpn_expression); "
" ";
std::string rpn_expression;
char_process<T,is_digit_func<T>> isdigit;
char_process<T,to_num_func<T>> tonum;
exprtk::rtl::io::println<T> println;
symbol_table_t symbol_table;
symbol_table.add_stringvar("rpn_expression", rpn_expression);
symbol_table.add_function ("println" , println );
symbol_table.add_function ("is_digit" , isdigit );
symbol_table.add_function ("to_num" , tonum );
expression_t expression;
expression.register_symbol_table(symbol_table);
parser_t parser;
parser.compile(rpn_program, expression);
const std::string rpn_expressions[] =
{
"2 3 8 / ^ 4 6 * + 3 9 / -", // 2 ^ (3 / 8) + 4 * 6 - 3 / 9
"1 2 / 6 5 2 - / * 7 +" , // (1 / 2) * (6 / (5 - 2)) + 7
"1 2 * 3 / 4 * 5 / 6 *" , // ((((1 * 2) / 3) * 4) / 5) * 6
"8 6 4 + * 2 /" // (8 * (6 + 4)) / 2
};
for (std::size_t i = 0; i < sizeof(rpn_expressions) / sizeof(std::string); ++i)
{
rpn_expression = rpn_expressions[i];
expression.value();
}
}
int main()
{
rpn_example<double>();
return 0;
}
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