How can I break the reading this text file (using ifstream)? C++

Question

Hi, I wanna stop the reading of my text input file when the word "synonyms" appears. I'm using ifstream and I don't know how to break the loop. I tried using a stringstream "synonyms" but it ended up junking my bst. I included the complete project files below in case you wanna avoid typing.

Important part:

 for(;;)  /*here, I wanna break the cycle when it reads "synonyms"*/
               {

               inStream >> word;
               if (inStream.eof()) break;

               wordTree.insert(word);
               }

               wordTree.graph(cout);

dictionary.txt

   1 cute
    2 hello
    3 ugly
    4 easy
    5 difficult
    6 tired
    7 beautiful
    synonyms
    1 7
    7 1
    antonyms
    1 3
    3 1 7
    4 5
    5 4
    7 3

Project.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

#include "MiBST.h"

using namespace std;

class WordInfo{

      public:
      //--id accesor
      int id ()const {return myId; } 

      /* myId is the number that identifies each word*/

      //--input function
      void read (istream &in)
      {
        in>>myId>>word;     
      }

      //--output function
      void print(ostream &out)
      {
          out<<myId<<" "<<word;     
      }

      //--- equals operator
     bool operator==(const WordInfo & otherword) const
     { return myId == otherword.myId; }

     //--- less-than operator
      bool operator<(const WordInfo & otherword) const
      { return myId < otherword.myId; }


      private:
              int myId;
              string word;

      };

      //--- Definition of input operator
      istream & operator>>(istream & in, WordInfo & word)
      {
           word.read(in);
      }

      //---Definition of output operator

      ostream & operator <<(ostream &out, WordInfo &word)
      {
            word.print(out);       
      }

      int main(){

          // Open stream to file of ids and words
          string wordFile;

          cout << "Enter name of dictionary file: ";
          getline(cin, wordFile);

          ifstream inStream(wordFile.data());



          if (!inStream.is_open())
          {
           cerr << "Cannot open " << wordFile << "\n";
           exit(1);
          }


          // Build the BST of word records
          BST<WordInfo> wordTree;   // BST of word records

          WordInfo word;            // a word record



          for(;;)  /*here, I wanna break the cycle when it reads "synonyms"*/
           {

           inStream >> word;
           if (inStream.eof()) break;

           wordTree.insert(word);
           }

           wordTree.graph(cout);

           //wordTree.inorder(cout);


          system ("PAUSE");
          return 0;

      }

MiBST.h (in case you wanna run it)

#include <iostream>
#include <iomanip>

#ifndef BINARY_SEARCH_TREE
#define BINARY_SEARCH_TREE




template <typename DataType>
class BST
{
 public:
  /***** Function Members *****/
  BST();

  bool empty() const;

  bool search(const DataType & item) const;

  void insert(const DataType & item);

  void remove(const DataType & item);

  void inorder(std::ostream & out) const;

  void graph(std::ostream & out) const;

  private:
  /***** Node class *****/
  class BinNode 
  {
   public:
    DataType data;
    BinNode * left;
    BinNode * right;

    // BinNode constructors
    // Default -- data part is default DataType value; both links are null.
    BinNode()
    : left(0), right(0)
    {}

    // Explicit Value -- data part contains item; both links are null.
    BinNode(DataType item)
    : data(item), left(0), right(0)
    {}


}; //end inner class

typedef BinNode * BinNodePointer; 

  /***** Private Function Members *****/
  void search2(const DataType & item, bool & found,
               BinNodePointer & locptr, BinNodePointer & parent) const;
 /*------------------------------------------------------------------------
   Locate a node containing item and its parent.

   Precondition:  None.
   Postcondition: locptr points to node containing item or is null if 
       not found, and parent points to its parent.#include <iostream>
 ------------------------------------------------------------------------*/

  void inorderAux(std::ostream & out, 
                  BST<DataType>::BinNodePointer subtreePtr) const;
  /*------------------------------------------------------------------------
    Inorder traversal auxiliary function.

    Precondition:  ostream out is open; subtreePtr points to a subtree 
        of this BST.
    Postcondition: Subtree with root pointed to by subtreePtr has been
        output to out.
 ------------------------------------------------------------------------*/

  void graphAux(std::ostream & out, int indent,
                      BST<DataType>::BinNodePointer subtreeRoot) const;
  /*------------------------------------------------------------------------
    Graph auxiliary function.

    Precondition:  ostream out is open; subtreePtr points to a subtree 
        of this BST.
    Postcondition: Graphical representation of subtree with root pointed 
        to by subtreePtr has been output to out, indented indent spaces.
 ------------------------------------------------------------------------*/

 /***** Data Members *****/
  BinNodePointer myRoot; 

}; // end of class template declaration

//--- Definition of constructor
template <typename DataType>
inline BST<DataType>::BST()
: myRoot(0)
{}

//--- Definition of empty()
template <typename DataType>
inline bool BST<DataType>::empty() const
{ return myRoot == 0; }

//--- Definition of search()
template <typename DataType>
bool BST<DataType>::search(const DataType & item) const
{
   typename BST<DataType>::BinNodePointer locptr = myRoot;

   typename BST<DataType>::BinNodePointer parent =0;

/*   BST<DataType>::BinNodePointer locptr = myRoot;
   parent = 0; */ //falta el typename en la declaracion original

   bool found = false;
   while (!found && locptr != 0)
   {
      if (item < locptr->data)       // descend left
        locptr = locptr->left;
      else if (locptr->data < item)  // descend right
        locptr = locptr->right;
      else                           // item found
        found = true;
   }
   return found;
}

//--- Definition of insert()
template <typename DataType>
inline void BST<DataType>::insert(const DataType & item)
{
   typename BST<DataType>::BinNodePointer 
        locptr = myRoot,   // search pointer
        parent = 0;        // pointer to parent of current node
   bool found = false;     // indicates if item already in BST
   while (!found && locptr != 0)
   {
      parent = locptr;
      if (item < locptr->data)       // descend left
         locptr = locptr->left;
      else if (locptr->data < item)  // descend right
         locptr = locptr->right;
      else                           // item found
         found = true;
   }
   if (!found)
   {                                 // construct node containing item


      locptr = new typename BST<DataType>::BinNode(item);  
      if (parent == 0)               // empty tree
         myRoot = locptr;
      else if (item < parent->data )  // insert to left of parent
         parent->left = locptr;
      else                           // insert to right of parent
         parent->right = locptr;
   }
   else
      std::cout << "Item already in the tree\n";
}

//--- Definition of remove()
template <typename DataType>
void BST<DataType>::remove(const DataType & item)
{
   bool found;                      // signals if item is found
   typename BST<DataType>::BinNodePointer 
      x,                            // points to node to be deleted
      parent;                       //    "    " parent of x and xSucc
   search2(item, found, x, parent);

   if (!found)
   {
      std::cout << "Item not in the BST\n";
      return;
   }
   //else
   if (x->left != 0 && x->right != 0)
   {                                // node has 2 children
      // Find x's inorder successor and its parent
      typename BST<DataType>::BinNodePointer xSucc = x->right;
      parent = x;
      while (xSucc->left != 0)       // descend left
      {
         parent = xSucc;
         xSucc = xSucc->left;
      }

     // Move contents of xSucc to x and change x 
     // to point to successor, which will be removed.
     x->data = xSucc->data;
     x = xSucc;
   } // end if node has 2 children

   // Now proceed with case where node has 0 or 2 child
   typename BST<DataType>::BinNodePointer 
      subtree = x->left;             // pointer to a subtree of x
   if (subtree == 0)
      subtree = x->right;
   if (parent == 0)                  // root being removed
      myRoot = subtree;
   else if (parent->left == x)       // left child of parent
      parent->left = subtree; 
   else                              // right child of parent
      parent->right = subtree;
   delete x;
}

//--- Definition of inorder()
template <typename DataType>
inline void BST<DataType>::inorder(std::ostream & out) const
{ 
   inorderAux(out, myRoot); 
}

//--- Definition of graph()
template <typename DataType>
inline void BST<DataType>::graph(std::ostream & out) const
{ graphAux(out, 0, myRoot); }

//--- Definition of search2()
template <typename DataType>
void BST<DataType>::search2(const DataType & item, bool & found,
                            BST<DataType>::BinNodePointer & locptr, 
                            BST<DataType>::BinNodePointer & parent) const
{
   locptr = myRoot;
   parent = 0;
   found = false;
   while (!found && locptr != 0)
   {
      if (item < locptr->data)       // descend left
      {
         parent = locptr;
         locptr = locptr->left;
      }
      else if (locptr->data < item)  // descend right
      {
         parent = locptr;
         locptr = locptr->right;
      }
      else                           // item found
         found = true;
   }
}
//--- Definition of inorderAux()
template <typename DataType>
void BST<DataType>::inorderAux(std::ostream & out, 
                               BST<DataType>::BinNodePointer subtreeRoot) const
{
   if (subtreeRoot != 0)
   {
      inorderAux(out, subtreeRoot->left);    // L operation
      out << subtreeRoot->data << "  ";      // V operation
      inorderAux(out, subtreeRoot->right);   // R operation
   }
}


//--- Definition of graphAux()


template <typename DataType>
void BST<DataType>::graphAux(std::ostream & out, int indent, 
                             BST<DataType>::BinNodePointer subtreeRoot) const
{
  if (subtreeRoot != 0)
    {
      graphAux(out, indent + 8, subtreeRoot->right);
      out << std::setw(indent) << " " << subtreeRoot->data << std::endl;
      graphAux(out, indent + 8, subtreeRoot->left);
    }
}


#endif

Answer 1

You should make an operator == on WordInfo to compare it to a string, then you can just this in the reading loop:

if ( word == "synonyms" ) break;

Answer 2

You can do it like

/* here, it stops when reading "synonyms" or when failing to extract a word. */
while(inStream >> word && word != "synonym") {
    wordTree.insert(word);
}
wordTree.graph(cout);

Note that when it fails to read a sequence of non-whitespace characters, it sets the fail-bit of the stream. inStream evaluates to false then. That is what makes the loop work. Be careful when using .eof(); It only returns true after you tried to read beyond the end of file. So for example, you will exit the loop, and miss the word 3 tree here:

1 house 2 garden 3 tree

Assuming there is no white-space after tree. The same will of course happen if you have newlines between the word information and have no trailing newline after the last word. Using if(inStream) (which the while loop does implicitly) is safe. It would still evaluate to true in this case, and only to false if it didn't read anything except white-space.

Answer 3

@SoapBox:

I created this == operator:

 //--- equals operator for String
     bool operator==(const string & aString) const
     { return word == aString; } // word is the WordInfo string field for 'real' word

And changed the for(;;) to:

for(;;)
           {


           inStream >> word;
           if (word=="synonyms") break;

           wordTree.insert(word);
           }

And ended up with an infinite loop printing:

"Item already in the tree"

Btw, I previoulsy tested the tree with a sample dictionary like this and it worked.

dict2.txt

1 cute 2 hello 3 ugly 4 easy 5 difficult 6 tired 7 beautiful