C++ retrieving pointer from stack

Question

I have class with this format:

class polarity {
public:
    void method1();
    void method2();


    polarity();
    ~polarity();
private:

    stack<type*>  carbon;
    vector<scientist*>   sci;

};

here is method1:

void polarity::method1(){

    type * object1;
    object1 = new type();
    unsigned int i;


        for(i = 0; i <carbon.size() ; ++i){         
            object1 = carbon.pop();
            /*Do something with object1*/
        }
}

when I run the program I receive this error

Error   1   error C2440: '=' : cannot convert from 'void' to 'type *'

I do not understand what it means. I just fill stack with some pointer of type. but I cannot retrieve these pointer.
I would appreciate for any help.

Take a look at the documentation for std::stack... A quick search will tell you what the top() and the pop() functions do. — Ivaylo Valchev
– Ivaylo Valchev, Commented Oct 18, 2016 at 22:04

YosefMac · Accepted Answer · 2016-10-18 22:06:38Z

4

The method pop from stack return a void because only pop out the element from the stack maybe you looking for carbon.top() but I don't know what you are trying to achieve

answered Oct 18, 2016 at 22:06

YosefMac

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Comments

amanuel2 · Accepted Answer · 2016-10-18 22:06:28Z

2

pop() function is a void function:

void pop();

Removes the top element from the stack. Effectively calls c.pop_back().

Therefore when you assign a type* to a function returning void, you get that error.

As you can see here:

  object1 = carbon.pop();

when you pop carbon you return a void , which is not of type type. Hence getting the error :

Error 1 error C2440: '=' : cannot convert from 'void' to 'type *'

Look here for refrence

Solution

You are looking for top() . so now you can do :

  object1 = carbon.top();

Look here for refrence about top().

answered Oct 18, 2016 at 22:06

amanuel2

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1 Comment

amanuel2 Over a year ago

Can someone please explain why the downvote, So i can improve my answer? Thankyou

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