CODEWITHSUNDEEP
c++
D1X
D1X

Reputation: 5474

stack of arrays usage (argument passing/returning)

I have to work on several functions that need to have as argument a stack of arrays.

This is the example:

using namespace std;

typedef vector<array<array<short,2>,64>> dmat;
typedef stack<array<short,2>> lifo;
typedef array<short,2> array2;

    array2 posible(lifo& pila, int j){   // Gets the stack by reference
                    array2 ret=pila.top();
                    return ret;     
    }

The questions are:

Upvotes: 0

Views: 84

Answers (2)

Mike Seymour
Mike Seymour

Reputation: 254631

Is this correct? I mean, can I assign and return the element in my stack that way?

Now you've changed the type to match, yes. This will return a copy (not a reference) of the array on top of the stack.

In the original question, no; as I'm sure your compiler would have said. There's no implicit conversion between an array of short (which top() gives you) and an array of int (which you try to assign that to). You can return the same array type by value or reference; or write a little conversion function if you need to change the type for some reason.

Is this correct? sol[0]=lifo;

No; again, the compiler should have told you. You're trying to assign a stack to an array. Change the type of dmat to vector<lifo>, and you can copy a lifo into it.

Is this syntax pila.top()[1] legal?

Yes, that gives the second element of the array on top of the stack. top() returns a reference to that array, which [1] can index.

Upvotes: 1

TartanLlama
TartanLlama

Reputation: 65720

No, this is not valid because the types of array2 and decltype(pila.top()) are disparate: array<short,2> cannot be implicitly converted to an array<int,2>. If you change the type of array2 then your program will be semantically correct.

No, sol[0] = lifo is not valid as you are trying to assign a stack to an array

Yes, pila.top()[1] returns the second element of the array at the top of the stack.

Upvotes: 0

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