I can't figure out why

[jturner38]

The only problem Im having is that my program always displays "Unmatched grouping symbols". I know its in my main program in my while loop. I just cant figure out what's causing it. I've tried to use the Debugger but I dont understand what too look for.

#include <iostream>
using namespace std;

const int DefaultListSize = 50;
typedef char Elem;

class Astack 
{
private:
	int top;	/*Index for top element*/
	int size;	/*Maximum size of stack*/
	Elem*listArray;	/*Array holding stack elements*/
public:	
		Astack(int sz =DefaultListSize)	/*Constructor*/
		{size = sz; top = 0; listArray = new Elem[sz];}
		~Astack() { delete [] listArray;}	/*Destructor*/
		void clear() {top = 0;}
		bool push(const Elem& item){
			if(top == size) return false;	/* Stack is full*/
			else {listArray [top++] = item;
				return true;
			}
		}
		bool pop(Elem& item){	/*Pop top element*/
			if(top == 0) return false;
			else {item = listArray[--top]; 
				return true;
			}
		}
		bool topValue(Elem& item) const {	/*Return top element*/
			if (top == 0) return false;
			else {item = listArray[top - 1];
			return true;
			}
		}
		int length() const {return top;}
		bool IsEmpty() const {if(top == 0) return true;
		else return false;
		}
	};

	bool Opener(char ch){
	 if((ch == '(') || (ch =='[') || (ch =='{'))
		return true;
	else 
		return false;
	}/*end of opener*/

	bool Match(char Lc, char Rc){
		if(( Lc == '(') && (Rc == ')') || ((Lc == '[') && (Rc == ']')) ||((Lc == '{') && (Rc == ']')))
			return true;
		else
			return false;
	}/*end of Match*/

	bool Closer(char ch){
		if((ch == ')') || (ch == ']') || (ch == '}'))
			return true;
		else
			return false;
	}/*end of closer*/

int main(){
	
	Astack S;
	char s;

cout <<"Enter data:";
cin >> s;

if(Opener(s)){ 
	S.push (s);
	}
else
	cin.ignore(s);

if(Closer(s)){
	S.pop(s);
}

while(S.pop(s)){
	if(Match(Opener(s), Closer(s)))
		cout << "Grouping symbols used properly";
	
	else 
		cout << "Unmatched grouping symbols";
}

}

[bithub]

Match() takes 2 chars, but you are passing in 2 bools instead.

[jturner38]

Oh I think I know what u mean

while(S.pop(s)){
	if(Match('(', ')') || ('[', ']') || ('{', '}'))
		cout << "Grouping symbols used properly";
	
	else 
		cout << "Unmatched grouping symbols";
}

The problem with this tho is that it always displays "Grouping symbols used properly". So maybe I need &&'s instead of ||'s?

[jturner38]

I changed it to this but Im still having the same problem. Is it because Im missing a part that somehow suppose to compare how many openers and closers I have. Which means if I have at least 1 or more than the other than I will display "Unmatched grouping symbols" ?

while(S.pop(s)){
	if(Match('(',')') || Match('[', ']') || Match('{', '}'))
		cout << "Grouping symbols used properly";
	
	else 
		cout << "Unmatched grouping symbols";
}

[Salem]

You pop a character.
If it's a (, then you need to match it with a )
It's no good trying to match it with a ]

[jturner38]

Oooh wait let me see...so instead of saying S.pop(s)...should it be S.pop(')') then check it in to see if its a match? When u say You pop a CHARACTER...u mean what Im actually poppin off the stack right?

[Salem]

Yes, pop() returns (via the reference parameter), the character at the top of the stack.

So if you're looking at a ) in your string, you should be expecting to pop a (

[jturner38]

Ok I think I see what u mean but isnt a rule for the Stack first one in is the last one out? So wouldnt I always pop a Closer? I tried this:

S.pop('(');

But I get an error: initial value of reference to non-const must be an lvalue. An lvalue means you can use the object on the left of an assignment operator correct? If thats true then what would I assign the bracket to?

[Salem]

You pop into a variable, then compare two things...

[jturner38]

I got it finally. Here my final code if anybody wants to check it out:

#include <iostream>
#include <string>
using namespace std;


const int DefaultListSize = 50;
typedef char Elem;

class Astack 
{
private:
	int top;	/*Index for top element*/
	int size;	/*Maximum size of stack*/
	Elem*listArray;	/*Array holding stack elements*/
public:	
		Astack(int sz =DefaultListSize)	/*Constructor*/
		{size = sz; top = 0; listArray = new Elem[sz];}
		~Astack() { delete [] listArray;}	/*Destructor*/
		void clear() {top = 0;}
		bool push(const Elem& item){
			if(top == size) return false;	/* Stack is full*/
			else {listArray [top++] = item;
				return true;
			}
		}
		bool pop(Elem& item){	/*Pop top element*/
			if(top == 0) return false;
			else {item = listArray[--top]; 
				return true;
			}
		}
		bool topValue(Elem& item) const {	/*Return top element*/
			if (top == 0) return false;
			else {item = listArray[top - 1];
			return true;
			}
		}
		int length() const {return top;}
		bool IsEmpty() const {if(top == 0) return true;
		else return false;
		}
	};

	bool Opener(char ch){
	 if((ch == '(') || (ch =='[') || (ch =='{'))
		return true;
	else 
		return false;
	}/*end of opener*/

	bool Match(char Lc, char Rc){
		if(( Lc == '(') && (Rc == ')') || ((Lc == '[') && (Rc == ']')) ||((Lc == '{') && (Rc == '}')))
			return true;
		else
			return false;
	}/*end of Match*/

	bool Closer(char ch){
		if((ch == ')') || (ch == ']') || (ch == '}'))
			return true;
		else
			return false;
	}/*end of closer*/


int main(){
	
	Astack S;
	string s;
	unsigned int i;
	char a;

	cout <<"Enter data:\n";
	getline(cin, s);

	for(i = 0; i < s.length(); i++){
		if(Opener(s.at(i)))
			S.push(s.at(i));

		else if(Closer(s.at(i))){
			if(S.IsEmpty()){
				cout << "Found a Closing bracket before an Opening bracket or\n There are no Opening brackets or\n There's an extra Closing bracket";
				cout << "\nGrouping symbols not used properly";
				return 0;
			}
			else 
				S.pop(a);
				if(!Match(a, s.at(i))){
					cout << "No matching bracket\n";
					cout << "Grouping symbols not used properly";
					return 0;
				}		
		}
	}
	if(!S.IsEmpty()){
		cout << "There's still an Opening bracket\n";
		cout << "Grouping symbols not used properly";
	}
	else
		cout << "Grouping symbols were used properly";
	return 0;
}