[C++]This as default parameter

Question

I want to write a recursive function that gives me the lenght of a list. To make it recursive, i use this pointer as default parameter in the declaration of the function in the List class header. But the compiler gives me an error... This is the code:

//Header file
#include "Nodo.h"

template < class Tipo >

class Lista
{

    private:
        Nodo< Tipo >* Prox; 

    public:
        Lista();

        bool ListaVuota();

        int DimensioneLista(Lista<Tipo>* = this);

        void InserisciInCoda(Tipo);

};

//CPP file

template< class Tipo >

int Lista< Tipo >::DimensioneLista(Lista< Tipo >* lista)

{

    if(lista->ListaVuota())
        return 0;
    else
        return 1+DimensioneLista(lista);

}

What error and in what line? – Philipp Oct 22 '13 at 09:56 — Philipp, Oct 22 '13 at 09:56

score 5 · Answer 1 · answered Oct 22 '13 at 09:56

5

Yes, this can only be used within functions.

The simplest change would be to use NULL as your default value instead, then check for NULL in your function, and use this instead

answered Oct 22 '13 at 09:56

benjymous

2,102
1
14
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5

Simpler still, an overload, so there's no need for a runtime check: `int DimensioneLista() {return DimensioneLista(this);}` – Mike Seymour Oct 22 '13 at 09:59
@MikeSeymour You might want to make this a separate answer. – Angew is no longer proud of SO Oct 22 '13 at 10:03

[C++]This as default parameter

1 Answers1