exprtk_gcd.cpp

/*
 **************************************************************
 *         C++ Mathematical Expression Toolkit Library        *
 *                                                            *
 * ExprTk Greatest Common Divisor Example                     *
 * Author: Arash Partow (1999-2023)                           *
 * 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                    *
 *                                                            *
 **************************************************************
*/


#include <cstdio>
#include <iostream>
#include <string>

#include "exprtk.hpp"


template <typename T>
inline T gcd_println(T x, T y, T z)
{
   printf("gcd(%2d,%2d) = %2d\n",
          static_cast<int>(x),
          static_cast<int>(y),
          static_cast<int>(z));

   return T(0);
}

template <typename T>
void gcd()
{
   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;

   symbol_table_t symbol_table;
   symbol_table.add_function("println",gcd_println);

   compositor_t compositor(symbol_table);
   compositor
      .add(
      function_t( // define function: gcd(x,y)
           "gcd",
           " switch                        "
           " {                             "
           "   case 0 = x : 0;             "
           "   case 0 = y : x;             "
           "   case x = y : x;             "
           "   case x > y : gcd(x - y, y); "
           "   default    : gcd(x, y - x); "
           " }                             ",
           "x","y"));

   const std::string gcd_program =
                     " i := 0;                      "
                     " while ((i += 1) < 100)       "
                     " {                            "
                     "   j := 0;                    "
                     "   repeat                     "
                     "     println(i, j, gcd(i,j)); "
                     "   until ((j += 1) >= 100);   "
                     " };                           ";

   expression_t expression;
   expression.register_symbol_table(symbol_table);

   parser_t parser;
   parser.enable_unknown_symbol_resolver();
   parser.compile(gcd_program,expression);

   expression.value();
}

int main()
{
   gcd<double>();
   return 0;
}