asked on

struct in C++ ......

To C++ Expert,

I got a code as follows :
------------------
struct A{
A(A* a_ptr){ cout << "woof" << endl;}
} ;

A* A(A* a_ptr){ cout <<"meow" << endl ;}

struct A* a1=A(0) ; //line 1
struct A* a2 = new struct A(0) ; //line 2
struct A a3 = A(0) ; //lin3
------------------
The code does compile and work. But I don't understand :

1. How come the function "A* A(A* a_ptr)" can
take "0" as an argument ? i.e. How come line 1
works ?
2. How come it is "new struct A(0)" not "new A(0)" ?
Also, how come the constructor "A(A* a_ptr)"
can take "0" as an argument ? i.e. How come
line 2 works ?

Thanks a lot !!!

ASKER CERTIFIED SOLUTION

jcwlc

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yasser_helmy

In C++ (as in C), 0 represents NULL.. the type conversion between int and A* is done automatically..

I think in c++, you can use both syntax; you can use "new struct A(0)" and/or"new A(0)".. try it and see if it works.. :)

meow00

ASKER

Hi,

I tried "struct foo f4 = new f00(0)" and "foo f4 = new f00(0)",
neither of them compiles. I don't understand that why it works for class but not for struct ....?? Thanks.

meow ......

SOLUTION

yasser_helmy

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yasser_helmy

accept an answer please