Help: Storing tokenized 2-digit char (infix->postfix converter)

Hi,

I'm trying to store a tokenized cstring (consisting of a mathematical expression) into a templated char stack. However, when I print the contents of the stack, the char tokens that represented 2-digit int were cut off after the first digit. Here's an example:

Code:

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Input:    12 + 14
Output:  1 + 1

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I expected this. Can I get help trying to store 2-digit tokens into the stack? Perhaps convert it so I can use the tokens later to calculate in RPN?

Here's the code that stores a cstring into the stack:

Code:

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void Stack<E>::str2Stack(char cstring[])
{
        char* token;
        token = strtok(cstring, " \n");
        while (token != NULL)
        {
                push(*token);
                cout<<"Token "<<token<<" pushed"<<endl;
                token = strtok(NULL, " \n");
        }
}

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Thank you!

Code:

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push(*token);

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pushes a single character. You want to allocate enough space to hold strlen(token) + 1, and then pass a pointer to this new memory to push(). I think.

Better yet, use std::string! Unless this project has severe space limitations, your life will be sweeter if you use std::string and stringstream.

What are your exact requirements for this assignment? This is important for us to know as you are mixing C and C++ here, which is generally not a good idea unless you are required to. As for some ideas:

1. You are going to need to know about the Shunting yard Algorithm
2. Char arrays should be avoided, you could use std::string here instead.
3. Strtok is a C function, you should be using std::stringstream for tokenizing.
4. Unless you are required to create your own stack class, use std::stack.

That is about all I can say until you let is know what your exact requirements are.

Quote:

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Originally Posted by AndrewHunter

You are going to need to know about the Shunting yard Algorithm

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I read up on it before the project, and I incorporated it into my program.

Quote:

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Originally Posted by AndrewHunter

Char arrays should be avoided, you could use std::string here instead. Strtok is a C function, you should be using std::stringstream for tokenizing

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This was my first thought. I turned to c strings as a suggestion from the professor, though.

Quote:

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Originally Posted by AndrewHunter

Unless you are required to create your own stack class, use std::stack.

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I was.


Here is my infix->postfix function

Code:

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template <typename E>
Stack<E> Stack<E>::infix2Post() throw(MismatchedParen)
{
        Stack<char> opStk(50);
        Stack<char> outStk(50);
        int i=0;

        while(isOperator(S[i])||isOperand(S[i])||S[i]=='('||S[i]==')')
        {
                if(isOperand(S[i]))
                {
                        outStk.push(S[i]);
                        i++;
                }
                if(isOperator(S[i]))
                {       
                        while((!opStk.empty())&&((S[1]!='^'&& precedence(S[i])<=precedence(opStk.top()))||
                                (S[1]=='^'&&precedence(S[i])<precedence(opStk.top()))))

                                {
                                        outStk.push(opStk.top());
                                        opStk.pop();
                                }
                        opStk.push(S[i]);
                        i++;
                }

                if(S[i]=='(')
                {
                        opStk.push('(');
                        i++;
                }

                if(S[i]==')')
                {
                        while(opStk.top()!='(')
                        {
                                outStk.push(opStk.top());
                                opStk.pop();
                        }

                        if(opStk.top()=='(')
                        {
                                opStk.pop();
                                i++;       
                        }

                        if(opStk.empty())
                                throw MismatchedParen("No closing parenthesis");

       
                }

        }

        while(!(opStk.empty()))
        {
                if(opStk.top()=='(' || opStk.top()==')')
                        throw MismatchedParen("No closing parenthesis");
                outStk.push(opStk.top());
                opStk.pop();
        }

        return outStk;

}

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And my driver:

Code:

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#include <iostream>
#include"Stack.h"
#include"Stack.cpp"                               
#include"Exception.h"
#include<string>
#include<cstring>
#include<cstdlib>
using namespace std;

#pragma warning( disable : 4290 )

int main()
{       
        char infix[50];
        char temp[50];
       
        Stack<char> inStk(50);


        cout<<"Enter an expression: ";
        cin.getline (infix, 50, '\n' );

        strcpy(temp, infix);

        cout<<infix<<endl;

        cout<<"NOW PRINTING LOCAL INFIX CHAR ARRAY"<<endl;
        char* token=NULL;
        token = strtok(temp, " \n");
        while (token != NULL)
        {
                cout<<token<<endl;
                token = strtok(NULL, " \n");
        }

        strcpy(temp, infix);

        cout<<"\nNOW PUSHING INFIX CHAR ARRAY TO INFIXSTACK CLASS ARRAY"<<endl;
        inStk.str2Stack(temp);

        cout<<"\n\nNOW PRINTING INFIXSTACK CLASS ARRAY"<<endl;

        inStk.printStack();

        strcpy(temp, infix);

        cout<<"\n\nNOW COPYING INFIXSTACK CLASS ARRAY TO POSTFIXSTACK CLASS ARRAY"<<endl;

        Stack<char> postStk(50);

        postStk=inStk;
       
        postStk.printStack();

        cout<<"\n\nNOW CONVERTING INFIXSTACK CLASS ARRAY TO POSTFIXSTACK CLASS ARRAY"<<endl;

        postStk=inStk.infix2Post();

        cout<<"\n\nNOW PRINTING POSTFIXSTACK CLASS ARRAY"<<endl;
        postStk.printStack();

        cout<<"\n\nNOW PRINTING EVALUATING POSTFIXSTACK CLASS ARRAY"<<endl;
        cout<<postStk.evalPost()<<endl;
        return 0;
}

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