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is_palindrome

This is a discussion on is_palindrome within the C++ Programming forums, part of the General Programming Boards category; I have written this program with the intention of identifiying palindrome words. Can someone spot why I am running into ...

  1. #1
    Tweaking master Aslaville's Avatar
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    is_palindrome

    I have written this program with the intention of identifiying palindrome words.
    Can someone spot why I am running into a segmentation fault ?
    Code:
    #include <vector>
    #include <iostream>
    #include <string>
    bool is_palindrome ( const std::string & s )
    {
      return equal ( s.begin(),s.end(),s.rbegin() );
    }
    std::istream & read ( std::istream & s , std::string& temp_store )
    {
      if ( s )
         while( s >> temp_store )
          return s;
    }
     std::vector< std::string > check_for_palindrome ( std::istream & s  )
    {
      std::vector < std::string > palindrome_words;
      
       std::string word_read;
       
      while( read ( s , word_read )){
      
        if ( is_palindrome ( word_read ) )
          palindrome_words.push_back(word_read);
      }
      return palindrome_words;
    }  
    int main ( int argc ,char * argv[] )
    { 
      std::vector < std::string > words_reported_palindrome;
      
      words_reported_palindrome = check_for_palindrome ( std:: cin );
      
      typedef std::vector < std::string > ::const_iterator iter;
      
      for ( iter my_iter = words_reported_palindrome.begin(); my_iter != words_reported_palindrome.end(); ++my_iter)
        
      {
        std::cout << *my_iter << std::endl;
        
      }
      return 0;
    }

  2. #2
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    Just run it through a debugger and backtrace where it crashes.
    It is too clear and so it is hard to see.
    A dunce once searched for fire with a lighted lantern.
    Had he known what fire was,
    He could have cooked his rice much sooner.

  3. #3
    Tweaking master Aslaville's Avatar
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    I had that but the problem was how to solve it.
    I rewrote the whole thing.Thanks for taking a look.
    Code:
    #include <vector>
    #include <iostream>
    #include <string>
    bool is_palindrome ( const std::string & s )
    {
      return equal ( s.begin(),s.end(),s.rbegin() );
    }
    std::istream & read ( std::istream & s , std::vector < std::string > &v )
    {
      if ( s ){
       std::string temp_store; 
        while ( s >> temp_store )
          if ( is_palindrome ( temp_store))
       v.push_back(temp_store);
      }
          return s;
    }
     /*std::vector< std::string > check_for_palindrome ( std::istream & s  )
    {
      std::vector < std::string > palindrome_words;
      
       std::string word_read;
       
      while( read ( s , word_read )){
      
        if ( is_palindrome ( word_read ) )
          palindrome_words.push_back(word_read);
      }
      return palindrome_words;
    }  */
    int main ( int argc ,char * argv[] )
    { 
      std::vector < std::string > words_reported_palindrome;
      
      //words_reported_palindrome =check_for_palindrome ( std:: cin );
      read ( std::cin , words_reported_palindrome );
      
      typedef std::vector < std::string > ::const_iterator iter;
      
      for ( iter my_iter = words_reported_palindrome.begin(); my_iter != words_reported_palindrome.end(); ++my_iter)
        
      {
        std::cout << *my_iter << std::endl;
        
      }
      return 0;
    }

  4. #4
    C++ Witch laserlight's Avatar
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    If you want to use std::equal, you should #include <algorithm>. Once you do that, you might also #include <iterator> then replace this:
    Code:
      typedef std::vector < std::string > ::const_iterator iter;
       
      for ( iter my_iter = words_reported_palindrome.begin(); my_iter != words_reported_palindrome.end(); ++my_iter)
         
      {
        std::cout << *my_iter << std::endl;
         
      }
    with:
    Code:
    std::copy(words_reported_palindrome.begin(),
              words_reported_palindrome.begin(),
              std::ostream_iterator<std::string>(std::cout, "\n"));
    By the way, I suggest that you indent consistently by more than a space. Personally, I prefer four spaces.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  5. #5
    "I Win!" by U. Lose vart's Avatar
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    Quote Originally Posted by laserlight View Post
    Code:
    std::copy(words_reported_palindrome.begin(),
              words_reported_palindrome.begin(),
              std::ostream_iterator<std::string>(std::cout, "\n"));
    should not the end() somewhere in this copy?
    To be or not to be == true

  6. #6
    C++ Witch laserlight's Avatar
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    Yes, copy and paste error.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  7. #7
    Tweaking master Aslaville's Avatar
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    Quote Originally Posted by laserlight View Post
    If you want to use std::equal, you should #include <algorithm>. Once you do that, you might also #include <iterator> then replace this:
    Code:
      typedef std::vector < std::string > ::const_iterator iter;
       
      for ( iter my_iter = words_reported_palindrome.begin(); my_iter != words_reported_palindrome.end(); ++my_iter)
         
      {
        std::cout << *my_iter << std::endl;
         
      }
    with:
    Code:
    std::copy(words_reported_palindrome.begin(),
              words_reported_palindrome.begin(),
              std::ostream_iterator<std::string>(std::cout, "\n"));
    By the way, I suggest that you indent consistently by more than a space. Personally, I prefer four spaces.
    Thanks very much.I am still awed by the power of the library.
    I got a bunch of errors when I replaced "\n" with '\n' (am such idiot , don't chuckle ) but I don't care bring them on.
    Last edited by Aslaville; 07-19-2013 at 03:34 AM.

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