Common Text Transformation Library http://cttl.sourceforge.net/

Mutable substring example

1. mutable_substring.cpp

• Program mutable_substring.cpp demonstrates mutable substring and text transformation during grammar evaluation:

Keywords: mutable_substring.cpp, edge, first( isdigit )

• 
  // sample code: mutable_substring.cpp
  // demonstrates cttl concept of a mutable substring
  
  //#define NDEBUG    // must appear before assert.h is included to stop assertions from being compiled 
  //#define CTTL_TRACE_EVERYTHING
  
  #include <iostream>
  #include "cttl/cttl.h"
  
  using namespace cttl;
  
  struct digit_parser {
  
      static size_t rule_digit( edge<>& edge_ )
      {
          return (
              +(
                  first( isdigit )
                  &
                  rule( digit_parser::event_digit )
              )
          ).match( edge_ );
      }
  
      static size_t event_digit( edge<>& edge_ )
      {
          // a single digit is found
          static const char* digits[] = {
              "zero;", "one;", "two;", "three;", "four;",
              "five;", "six;", "seven;", "eight;", "nine;"
          };
  
          size_t digit = edge_.first[ 0 ] - '0';
          assert( digit < ( sizeof( digits ) / sizeof( char ) ) );
          edge_.text( digits[ digit ] );
          return edge_.second.offset();
      }
  };
  
  int main(int argc, char* argv[])
  {
      if ( argc == 1 ) {
          std::cout
              << "Usage: on the command line, enter a "
              << std::endl
              << "number to convert its digits to words,"
              << std::endl
              << "for example:"
              << std::endl
              << '\t'
              << argv[ 0 ]
              << " 123"
              << std::endl
              ;
          return 1;
      }
  
      std::string inp = argv[ 1 ];
      edge<> substring( inp );
      if ( digit_parser::rule_digit( substring ) == std::string::npos ) {
          std::cout
              << "*** error *** no digits found at the beginning of the input"
              << std::endl
              ;
          return 1;
      }
  
      std::cout
          << inp
          << std::endl
          ;
      return 0;
  }
  
  

Copyright © 1997-2009 Igor Kholodov mailto:cttl@users.sourceforge.net.

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