intializing variables

This is a discussion on intializing variables within the C++ Programming forums, part of the General Programming Boards category; Here's par of my code: Code: bool Opener(char ch){ if((ch == '(') || (ch =='[') || (ch =='{')) return true; ...

  1. #1
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    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?

  2. #2
    Registered User whiteflags's Avatar
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    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.

  3. #3
    and the Hat of Guessing tabstop's Avatar
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    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.)

  4. #4
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    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;
    }

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    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.)

  6. #6
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    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.

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