On 10/23/14 1:03 AM, Shriramana Sharma via Digitalmars-d-learn wrote:
Hello. Please see the following code:
import std.stdio ;
struct Pair {
int x, y ;
this (int x, int y) { x = x ; y = y ; }
}
void main() {
auto P = Pair(1, 2) ;
writeln(P.x, ' ', P.y) ;
}
This outputs 0 0, whereas the equivalent C++ code outputs 1 2 correctly:
# include <iostream>
struct Pair {
int x, y ;
Pair(int x, int y) : x(x), y(y) {}
} ;
This is not the same. In the above, the x outside the parens is ALWAYS a
member. D does not have this syntax. Change it to the same as your D
implementation, and you get the same result (actually worse, because C++
will not initialize x and y for you).
int main() {
auto P = Pair(1, 2) ;
std::cout << P.x << ' ' << P.y << std::endl ;
}
It seems to me that D should either not permit argument names to
shadow the member names, since it has no initializer lists and all
members are automatically initialized. Comments?
You're missing the "or" part of that statement :)
But 2 things:
x = x;
This should produce an error, or at least a warning I think, as it does
nothing. However, even with dmd -w, it does not. I know I have seen the
compiler complain about noop statements before, I just don't know under
what circumstances
and 2, you would use the same mechanism as you use with C++ to
initialize the items inside the ctor:
this.x = x;
Note, the rules for shadowing are the same as for any function
parameters to any function vs. members or module variables. Nothing is
inconsistent here.
-Steve
