[RFernandez]

ill show exactly what the program is supposed to do:
Your program should read a character and determine
- if it is a new line, it is the end of the expression;
print the value at the top of the stack

- if it is a space, ignore it and continue with the next
iteration

- if it a digit, put it back on the input stream and read
an int number

- anything else should be an operator; your program should
them pop the top two elements on the stack, compute the
result, and push the result back on the stack

[#define]

You can put print statements in the code temporarily to debug eg

cout << "in loop" << endl;

and also print variables etc.

[RFernandez]

i tried that and i dont see much wrong with it, that i understand anyway.

[RFernandez]

anyone got anything? im lost

[#define]

If you print a message in the loop do you see that message.

In the switch you return values which means the program will end because you are in the main function. The variables a and b are not given a value.

In the third part you want to pop a value to a and pop a value to b. Instead of returning a value store the value and push it on to the stack.

[RFernandez]

the message does not appear. yeah i noticed that a and b didnt have a value. im trying to figure out what value to give them. i thought it would be stk.pop but i get an error with that. i believe it is stk.push for the value.

This post has been edited by RFernandez: 12 November 2014 - 05:51 PM

[RFernandez]

i gave a and b stk.top to see if that would work. and the program ran but still nothing happened. Its able to find my file but it seems its not able to execute anything

[RFernandez]

There seems to be something wrong with the first while loop. I put the cout message there and it doesnt get shown

[RFernandez]

here is my current code

#include    <iostream>
#include    <fstream>
#include    <cctype>
#include    <string>
#include    <stack>
using namespace std;

// function prototypes

ifstream& get_ifs(ifstream& ifs);


int main()
{
		
	ifstream ifs;	
	char c;   // input character
	if (!get_ifs(ifs))
	{ //File failed to open.
		return(1);
	}
	



	while ((c = ifs.peek()) != EOF)          // as long as there is input
	{
			

		stack< int > stk;                       // stack of ints
		stk.push(c);// handle one expression
		while ((c = ifs.get()) != '\n')
		{
			if (isspace(c))
			{
				

				putchar(c);
				c++;
				// handle whitespace character
			}
			else if (isdigit(c))             // is it a digit ?
			{
				

				ifs.putback(c);               // put it back in the input
				int number;                     // an incoming number
				ifs >> number;                  // read the number
				stk.push(number);
				cout << number << ' ';
			}
			else                               // it must be an operator
			{
				
				int a = stk.top();
				int b = stk.top();				
				switch (c) 
				{
				case '+':return a + b;
				case '-':return a - b;
				case '*':return a * b;
				case '/':return a / b;
					default: return 0; 
						cerr << "you have entered an incorrect operator" << '\n';
					
				}
				// handle operators +, -, *, and /
				// flag invalid operators
			}
		}

		cout << "result is " << stk.top() << '\n';
	}

	return 0;
}


ifstream& get_ifs(ifstream &ifs)                               // get input file stream
{
	string filename;                            // input file name
	

	cout << "name of file to read from? ";
	cin >> filename;
	ifs.open(filename.c_str());
	


	
	if (!ifs)                                 // cannot open file infilen
	{
		cerr << "cannot open input file '" << filename << "'\n";
	}

	return ifs;                                 // return input file stream

}

[#define]

You can try get_ifs returning a bool.

using namespace std;

// function prototypes
bool get_ifs(ifstream& ifs);


int main()
{
  ifstream ifs;	
  char c;   // input character

  if (!get_ifs(ifs))
  { //File failed to open.
    cout << "File failed to open" << endl;
    return(1);
  }

  cout << "after get_ifs" << endl;

The function has changed as well, to return true and false.

bool get_ifs(ifstream &ifs)  
{
  string filename;  

  cout << "name of file to read from? ";
  cin  >> filename;
  
  ifs.open(filename.c_str());

  if (!ifs)  
  {
    cerr << "cannot open input file '" << filename << "'\n";
    return false;
  }

  // fstream is ok
  return true;  
}

[RFernandez]

i do that and i get the message "after get ifs" and then the "press any key to continue"

[#define]

Did you try changing the variable c to a type int?

int main()
{
  ifstream ifs;	
  //char c;   // input character
  int c;

You can add a message in the outer loop.

while((c = ifs.peek()) != EOF)
{
  cout << "in peek loop" << endl;

[RFernandez]

changed the variable to int. When running the program "in peek loop" does not come up. so that seems to be where the problem is

[#define]

It probably best to check the stream in main, to see if that is ok.

cout << "after get_ifs" << endl;

if (ifs.good())
{
  cout << "stream is ok" << endl;
}
else
{
  cout << "stream is NOT ok" << endl;
}

[RFernandez]

stream is okay