Thread: intializing variables

Here's par of my code:

Code:

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

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;

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

	for(i = 0; i < s.length(); i++){
		if(Opener())
			S.push();
	}
		for(i = 0; i < s.length(); i++){
			if(Closer())
				S.pop();
			if(S.IsEmpty())
				cout << "No Openers found";
		}
		return 0;
}

Right now 4 functions dont take any arguments. If I put in variables then build the solution it gives me a warning stating that my variables are unintialized local variables. What does that mean?

The compiler actually should be giving you an error about too few arguments to Opener and Closer, which are the two functions I see.

If you are getting a warning about uninitialized local variables in addition to that, it means that one of the local variables you are using for its value was never assigned a value in the first place. The particular variable should be indicated by the line number of the warning. C++ does not initialize plain old data types (it will initialize user defined types if a default constructor is available) and their value in that case is undefined.

Notice that you shouldn't be putting in brand new variables in your function calls.

Code:

Opener(char ch) //NO
Opener(s[0]) //YES, as s already exists and is a string and therefore s[0] is a char

(EDIT: I mean when you call them, of course.)

The 4 functions are the Opener, Closer, push, and pop. Thats bc I havent put a variable in yet. But when I do it says that they are unintialized local variables. Which Im confused about.
Here is my whole code so far and Im a add variables so everyone can see :

Code:

#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;
                char b;

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

	for(i = 0; i < s.length(); i++){
		if(Opener(a))
			S.push(a);
	}
		for(i = 0; i < s.length(); i++){
			if(Closer(b))
				S.pop(a);
			if(S.IsEmpty())
				cout << "No Openers found";
		}
		return 0;
}

And why do you think a has a value when you call Opener(a)? HINT: It doesn't. (Well, it has some value, but it's garbage since you didn't put anything in there.)

In main, you don't initialize "a" and "b". Then you call "Opener(a)" but "a" is never set. Similarly you call "Closer(b)" but "b" is never set. Hence the warnings.