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binary tree postfix calculator

jamesfalter (12)
Hey guys, me again. This time around, I'm working on a binary tree calculator. Unfortunately, although my algorithms are most likely correct. it seems my grasp of c++ has failed me, and am getting compile errors like crazy, and am at my wits end as to what's wrong-which is a lot.
my code is below. can anyone assist me in spotting any glaring errors? Thanks!
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#include "TreeCalc.h"
#include <iostream>

using namespace std;

//Constructor
TreeCalc::TreeCalc()
{
 
  stack<TreeNode*> myStack;
}

//Destructor- frees memory
TreeCalc::~TreeCalc()
{
  cleanTree(myStack->top());
}

//Deletes tree/frees memory
void TreeCalc::cleanTree(TreeNode* ptr)
{
  if(ptr->value!=NULL){
    cleanTree(ptr->left);
    cleanTree(ptr->right);
  }
  else delete ptr;  
}

//Gets data from user
void TreeCalc::readInput()
{
    string response;
    cout << "Enter elements one by one in postfix notation" << endl
    << "Any non-numeric or non-operator character,"
    << " e.g. #, will terminate input" << endl;

    cout << "Enter first element: ";
    cin >> response;

    //while input is legal
    while (isdigit(response[0]) || response[0]=='/' || response[0]=='*'
            || response[0]=='-' || response[0]=='+' )
    {
        insert(response);
        cout << "Enter next element: ";
        cin >> response;
    }
}

//Puts value in tree stack
void TreeCalc::insert(const string& val)
{ 
  if(isdigit(val)){
    TreeNode* t=new TreeNode(val);
    myStack->push(t);
  }
  else{
    TreeNode* w=new TreeNode(val);
    w->right=myStack->top();
    myStack->pop();
    w->left=myStack->top();
    myStack->pop();
    myStack->push(w);
  }

}

//Prints data in prefix form
void TreeCalc::printPrefix(TreeNode* ptr) const
{
  if(ptr!=NULL){
    cout<<ptr->value;
    printPrefix(ptr->left);
    printPrefix(ptr->right);
}

//Prints data in infix form
void TreeCalc::printInfix(TreeNode* ptr) const
{
  if(ptr!=NULL){
    if(ptr->value=='+'||ptr->value=='-'||ptr->value=='*'||ptr->value=='/'){
      cout<<ptr->value;
      else {
	cout<<'(';
	printInfix(ptr->left);
	cout<<ptr->value;
	printInfix(ptr->right);
	cout<<ptr->')';
      }
    }
}

//Prints data in postfix form
void TreeCalc::printPostfix(TreeNode* ptr) const
{
  if(ptr!=NULL){
    printPostfix(ptr->left);
    printPostfix(ptr->right);
    cout<<ptr->value;
  }
}

// Prints tree in all 3 (pre,in,post) forms

void TreeCalc::printOutput() const
{
    if (mystack->size()!=0 && mystack->top()!=NULL)
    {
        cout << "Expression tree in postfix expression: ";
        // call your implementation of printPostfix()
	printPostfix(myStack->top());
        cout << endl;

        cout << "Expression tree in infix expression: ";
        // call your implementation of printInfix()
        printInfix(myStack->top());
        cout << endl;

        cout << "Expression tree in prefix expression: ";
        // call your implementation of printPrefix()
	printPrefix(myStack->top());
        cout << endl;
    }
    else
        cout<< "Size is 0." << endl;
}

//Evaluates tree, returns value
// private calculate() method
int TreeCalc::calculate(TreeNode* ptr) const
{
  if(ptr->left==NULL&&ptr->right==NULL)
    return atoi((ptr->value).c_str());
  else{
    int ret=0;
    switch(ptr->value){
    case '+':
      int l=calculate(ptr->left);
      int r=calculate(ptr->right);
      ret=l+r;
      break;
    case '-':
      int l=calculate(ptr->left);
      int r=calculate(ptr->right);
      ret=l-r;
      break;
    case '*':
      int l=calculate(ptr->left);
      int r=calculate(ptr->right);
      ret=l*r;
      break;
    case '/':
      int l=calculate(ptr->left);
      int r=calculate(ptr->right);
      ret=l/r;
      break;
    }
  return ret;
  }   



 
}

//Calls calculate, sets the stack back to a blank stack
// public calculate() method. Hides private data from user
int TreeCalc::calculate()
{
    int i = 0;
    // call private calculate method here
    i=calculate(myStack->top());
    return i;
}
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#ifndef TREENODE_H
#define TREENODE_H

#include <string>
using namespace std;

class TreeNode
{
public:
    TreeNode();						//Default Constructor
    TreeNode(const string & val);	//Constructor

private:
    string value;
    TreeNode *left, *right;			// for trees
    friend class TreeCalc;			//gives TreeCalc access to private data
};

#endif 
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#ifndef TREECALC_H
#define TREECALC_H
#include <stack>

#include "TreeNode.h"
using namespace std;

class TreeCalc
{
public:

    TreeCalc();						//Constructor
    ~TreeCalc();					//Destructor

    void cleanTree(TreeNode * ptr);	//Deletes tree/frees memory
    void readInput();				//gets data from user
    void insert(const string & val);	//puts value in tree

    // print methods
    void printPrefix(TreeNode * curNode) const;	//prints data in prefix form
    void printInfix(TreeNode * curNode) const;	//prints data in infix form
    void printPostfix(TreeNode * curNode) const;//prints data in postfix form
    void printOutput() const;				//prints in pre,in,post form
    int calculate();					//calls private calculate method

private:
    stack<int> myStack;
    int calculate(TreeNode* ptr) const;		//Evaluates tree, returns value

};

#endif 
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#include "TreeNode.h"

//Default Constructor -left and right are NULL, value '?'
TreeNode::TreeNode()
{
    value="?";
    left=NULL;
    right=NULL;
}

//Constructor - sets value to val
TreeNode::TreeNode(const string & val)
{
    value=val;
    left=NULL;
    right=NULL;
}

please note that TreeNode.cpp is not to be altered, and neither is readInput() in TreeCalc.cpp.
jim80y (264)
What compile errors?

Jim
jamesfalter (12)
the full list is as follows:
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TreeCalc.cpp: In destructor ‘TreeCalc::~TreeCalc()’:
TreeCalc.cpp:19:20: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp: In member function ‘void TreeCalc::cleanTree(TreeNode*)’:
TreeCalc.cpp:25:18: error: no match for ‘operator!=’ in ‘ptr->TreeNode::value != 0’
TreeCalc.cpp:25:18: note: candidates are:
/usr/include/c++/4.6/bits/stl_pair.h:214:5: note: template<class _T1, class _T2> bool std::operator!=(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
/usr/include/c++/4.6/bits/stl_iterator.h:297:5: note: template<class _Iterator> bool std::operator!=(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
/usr/include/c++/4.6/bits/stl_iterator.h:347:5: note: template<class _IteratorL, class _IteratorR> bool std::operator!=(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&)
/usr/include/c++/4.6/bits/allocator.h:132:5: note: template<class _T1, class _T2> bool std::operator!=(const std::allocator<_T1>&, const std::allocator<_T2>&)
/usr/include/c++/4.6/bits/allocator.h:137:5: note: template<class _Tp> bool std::operator!=(const std::allocator<_Tp1>&, const std::allocator<_Tp1>&)
/usr/include/c++/4.6/bits/stl_deque.h:259:5: note: template<class _Tp, class _Ref, class _Ptr> bool std::operator!=(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _Ref, _Ptr>&)
/usr/include/c++/4.6/bits/stl_deque.h:266:5: note: template<class _Tp, class _RefL, class _PtrL, class _RefR, class _PtrR> bool std::operator!=(const std::_Deque_iterator<_Tp, _RefL, _PtrL>&, const std::_Deque_iterator<_Tp, _RefR, _PtrR>&)
/usr/include/c++/4.6/bits/stl_deque.h:1943:5: note: template<class _Tp, class _Alloc> bool std::operator!=(const std::deque<_Tp, _Alloc>&, const std::deque<_Tp, _Alloc>&)
/usr/include/c++/4.6/bits/stl_stack.h:265:5: note: template<class _Tp, class _Seq> bool std::operator!=(const std::stack<_Tp, _Seq>&, const std::stack<_Tp, _Seq>&)
/usr/include/c++/4.6/bits/postypes.h:223:5: note: template<class _StateT> bool std::operator!=(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
/usr/include/c++/4.6/bits/basic_string.h:2473:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.6/bits/basic_string.h:2485:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.6/bits/basic_string.h:2497:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
/usr/include/c++/4.6/bits/streambuf_iterator.h:200:5: note: template<class _CharT, class _Traits> bool std::operator!=(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)
/usr/include/c++/4.6/ext/new_allocator.h:128:5: note: template<class _Tp> bool __gnu_cxx::operator!=(const __gnu_cxx::new_allocator<_Tp>&, const __gnu_cxx::new_allocator<_Tp>&)
/usr/include/c++/4.6/bits/stl_iterator.h:817:5: note: template<class _Iterator, class _Container> bool __gnu_cxx::operator!=(const __gnu_cxx::__normal_iterator<_Iterator, _Container>&, const __gnu_cxx::__normal_iterator<_Iterator, _Container>&)
/usr/include/c++/4.6/bits/stl_iterator.h:811:5: note: template<class _IteratorL, class _IteratorR, class _Container> bool __gnu_cxx::operator!=(const __gnu_cxx::__normal_iterator<_IteratorL, _Container>&, const __gnu_cxx::__normal_iterator<_IteratorR, _Container>&)
TreeCalc.cpp: In member function ‘void TreeCalc::insert(const string&)’:
TreeCalc.cpp:56:17: error: no matching function for call to ‘isdigit(const string&)’
TreeCalc.cpp:56:17: note: candidates are:
/usr/include/ctype.h:115:1: note: int isdigit(int)
/usr/include/ctype.h:115:1: note:   no known conversion for argument 1 from ‘const string {aka const std::basic_string<char>}’ to ‘int’
/usr/include/c++/4.6/bits/locale_facets.h:2566:5: note: template<class _CharT> bool std::isdigit(_CharT, const std::locale&)
TreeCalc.cpp:57:32: error: conversion from ‘TreeNode*’ to non-scalar type ‘TreeNode’ requested
TreeCalc.cpp:58:12: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp:61:32: error: conversion from ‘TreeNode*’ to non-scalar type ‘TreeNode’ requested
TreeCalc.cpp:62:6: error: base operand of ‘->’ has non-pointer type ‘TreeNode’
TreeCalc.cpp:62:21: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp:63:12: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp:64:6: error: base operand of ‘->’ has non-pointer type ‘TreeNode’
TreeCalc.cpp:64:20: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp:65:12: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp:66:12: error: base operand of ‘->’ has non-pointer type ‘std::stack<TreeNode*>’
TreeCalc.cpp: In member function ‘void TreeCalc::printPrefix(TreeNode*) const’:
TreeCalc.cpp:82:1: error: a function-definition is not allowed here before ‘{’ token
TreeCalc.cpp:177:1: error: expected ‘}’ at end of input
jim80y (264)
The first error says that in the TreeCalc::~TreeCalc destructor you're trying the use the pointer dereference operator '->' on something that's not a pointer.

If we look, you have

 
 
cleanTree(myStack->top());


Following to the declaration of myStack, we find that it's an actual object, not a pointer to an object. So, that code needs to be

 
 
cleanTree(myStack.top());


I see you've done throughout the code, so fix those up and then move on to the next error.

Which is saying that in TreeCalc::cleanTree it doesn't know how to compare TreeNode::value with zero.

 
 
if(ptr->value!=NULL){


If we look at the definition of TreeNode::value, it's a string object. You can't compare a string object with a number.

Don't get confused by what's returned when you dereference a pointer.
This code - ptr->value dereferences the ptr pointer and gets the value of the member called value. The actual value - which in this case is a string.

If you're using an empty string to mean "not-initialised" then you can probably just compare the string to "", rather than NULL (which is just another name for zero)

Fix those problems and your error list will be a bit shorter.

Jim
jamesfalter (12)
thanks man, this helped a lot.
jim80y (264)
No worries
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