exprtk_simple_example_09.cpp

/*
 **************************************************************
 *         C++ Mathematical Expression Toolkit Library        *
 *                                                            *
 * Simple Example 9                                           *
 * Author: Arash Partow (1999-2016)                           *
 * 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 Common Public License.         *
 * http://www.opensource.org/licenses/cpl1.0.php              *
 *                                                            *
 **************************************************************
*/


#include <cstdio>
#include <string>
#include "exprtk.hpp"


template <typename T>
void primes()
{
   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);

   symbol_table_t symbol_table;

   symbol_table.add_constants();
   symbol_table.add_variable("x",x);

   compositor_t compositor(symbol_table);

   //Mode 1 - if statement based
   compositor
      .add(
      function_t( // define function: is_prime_impl1(x,y)
           "is_prime_impl1",
           " if (y == 1,true,                "
           "    if (0 == (x % y),false,      "
           "       is_prime_impl1(x,y - 1))) ",
           "x","y"));

   compositor
      .add(
      function_t( // define function: is_prime1(x)
           "is_prime1",
           " if (frac(x) != 0, false,                                "
           "    if (x <= 0, false,                                   "
           "       is_prime_impl1(x,min(x - 1,trunc(sqrt(x)) + 1)))) ",
           "x"));

   //Mode 2 - switch statement based
   compositor
      .add(
      function_t( // define function: is_prime_impl2(x,y)
           "is_prime_impl2",
           " switch                                         "
           " {                                              "
           "   case y == 1       : true;                    "
           "   case (x % y) == 0 : false;                   "
           "   default           : is_prime_impl2(x,y - 1); "
           " }                                              ",
           "x","y"));

   compositor
      .add(
      function_t( // define function: is_prime2(x)
           "is_prime2",
           " switch                                                                 "
           " {                                                                      "
           "   case x <= 0       : false;                                           "
           "   case frac(x) != 0 : false;                                           "
           "   default           : is_prime_impl2(x,min(x - 1,trunc(sqrt(x)) + 1)); "
           " }                                                                      ",
           "x"));

   //Mode 3 - switch statement and while-loop based
   compositor
      .add(
      function_t( // define function: is_prime_impl3(x,y)
           "is_prime_impl3",
           " while (y > 0)                            "
           " {                                        "
           "   switch                                 "
           "   {                                      "
           "     case y == 1       : ~(y := 0,true);  "
           "     case (x % y) == 0 : ~(y := 0,false); "
           "     default           : y := y - 1;      "
           "   }                                      "
           " }                                        ",
           "x","y"));

   compositor
      .add(
      function_t( // define function: is_prime3(x)
           "is_prime3",
           " switch                                                                 "
           " {                                                                      "
           "   case x <= 0       : false;                                           "
           "   case frac(x) != 0 : false;                                           "
           "   default           : is_prime_impl3(x,min(x - 1,trunc(sqrt(x)) + 1)); "
           " }                                                                      ",
           "x"));

   std::string expression_str1 = "is_prime1(x)";
   std::string expression_str2 = "is_prime2(x)";
   std::string expression_str3 = "is_prime3(x)";

   expression_t expression1;
   expression_t expression2;
   expression_t expression3;
   expression1.register_symbol_table(symbol_table);
   expression2.register_symbol_table(symbol_table);
   expression3.register_symbol_table(symbol_table);

   parser_t parser;

   parser.compile(expression_str1,expression1);
   parser.compile(expression_str2,expression2);
   parser.compile(expression_str3,expression3);

   for (std::size_t i = 0; i < 100; ++i)
   {
      x = i;

      T result1 = expression1.value();
      T result2 = expression2.value();
      T result3 = expression3.value();

      printf("%03d  Result1: %c  Result2: %c  Result3: %c\n",
             static_cast<unsigned int>(i),
             (result1 == T(1)) ? 'T' : 'F',
             (result2 == T(1)) ? 'T' : 'F',
             (result3 == T(1)) ? 'T' : 'F');
   }
}

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