Im so close and Im stumped
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Thread: Im so close and Im stumped

  1. #1
    Join Date
    Nov 2010
    Posts
    36

    Im so close and Im stumped

    Write a program in C++ that checks various lines of text (taken as arithmetical expressions) to see if the following 3 pairs of grouping symbols: '(', ')'; '[', ']'; '{', '}' are being used properly.

    You must use a Stack with the array implementation using a class

    Test program on the following:

    a+b
    (a-b)
    ((c-d)
    [(a-b)*(c+d)]
    (e+f]
    (f+g))
    [f-g}
    {c+d)
    {a*[(c-d)*(e+f)+(g-h)/(f+g)]+h}*b+c
    (((((a)))))

    Code:
    #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);
    	}
    
    if(Closer(s)){
    	S.pop(s);
    }
    
    while(S.pop(s)){
    	if(Match)
    		cout << "Grouping symbols used properly";
    	else
    		cout << "Unmatched grouping symbols";
    }
    }
    I know I should take whatever I pop off the stack and then have Match check to see if if their are matches for each closer I pop. When I compile it just gives me everything is used properly which is incorrect.

  2. #2
    Join Date
    May 2006
    Location
    Dresden, Germany
    Posts
    458

    Re: Im so close and Im stumped

    The line
    Code:
        if(Match)
    is for sure not what you want.

    gcc says: "warning: the address of `bool Match(char, char)', will always evaluate as `true'"

    and IMHO it's right.

    "if (Match)" checks if Match is different from zero. Match is a function and you'll check the adress of the function here (which will always be different from zero).

    If you want to call Match use brackets ( ) and parameters.

    With regards
    Programartist
    Last edited by ProgramArtist; December 1st, 2010 at 02:59 AM.

  3. #3
    Join Date
    Nov 2010
    Posts
    36

    Re: Im so close and Im stumped

    Ok I finally figured it out. Thanks for the help. Now the problem is that it always displays "Unmatched grouping symbols".

    Code:
    #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";
    }
    }

  4. #4
    GCDEF is offline Elite Member Power Poster
    Join Date
    Nov 2003
    Posts
    12,047

    Re: Im so close and Im stumped

    Use the debugger to step through the Match function to see what it's doing.

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