Question

The title of the question is the error itself, but I will also include it below:

error: argument of type ‘char (CharStack::)()const throw (CharStack::Underflow)’ does not match ‘char’

Here is the code file that I am using:

#include <iostream>
#include "CharStack.h"
using namespace std;

// returns top value on stack
// throws exception if empty
//
// O(n)
char CharStack::top() const throw( Underflow )
{
    Elem * cur = head;

    if( !empty() )
    {
        while( cur && cur -> next )
            cur = cur -> next;

        return cur -> info;
    }
}


int main()
{
    CharStack * stack = new CharStack();

    char top = stack -> top;

    stack -> push( 't' );
    stack -> push( 'e' );
    stack -> push( 's' );
    stack -> push( 't' );
    stack -> push( 'i' );
    stack -> push( 'n' );
    stack -> push( 'g' );

    stack -> output( cout );

    delete stack;
}

In the header file I define the two exceptions I use, as an example I am following does:

     public:
     // exceptions
        class Overflow{};
        class Underflow{};

I assume it’s because I am not handling the excerption, but I do not how to handle it in this current situation.

Thank you

Answer 1

return cur -> info;

Is info a member function that returns a char? Then you should be using:

return cur -> info();

otherwise you’re returning a pointer-to-member-function, not a char.

Same for this:

char top = stack -> top;

stack->top is a member function pointer, stack->top() is a call to the top function of the stack object.

BTW, your top function doesn’t return anything if empty() is true, which is illegal. You need to either return a char, or throw, but leaving the function without returning or throwing is ill-formed.