On 7/19/16 11:25 AM, Rufus Smith wrote:
On Tuesday, 19 July 2016 at 06:46:44 UTC, Mike Parker wrote:
On Tuesday, 19 July 2016 at 06:32:32 UTC, Rufus Smith wrote:
Error: 'this' is only defined in non-static member functions, not
__lambda2
Lambda's are delegates and delegates have a "this" type of pointer. I
would like to get at it inside the lambda to check for some things.
I'm doing some funky stuff. I'm not concerned about the scope or what
this actually pointers to or anything like that, just need it's value
for debugging.
No, delegates do not have a "this" type of pointer. "this" is an
implicit function parameter in a class or struct member function.
Delegates have no such thing. The only generic way I know of to get at
a delegate's function pointer inside the implementation is to
explicitly add the pointer type to the parameter list as part of the
declaration and pass it as an argument when you call the delegate.
Delegates do have a this, they have a context pointer that is implicitly
passed and used to access the outside context. It is no different than
methods. Just because the explicit implementation details are different
does not change the underlying meaning.
I think what Mike may be alluding to is that there is no name for the
stack frame pointer you can use. There is no 'this' pointer that you can
get at (even though it can be passed).
Also note that lambdas are not necessarily delegates, they could be
straight function pointers if they don't need a context:
void main()
{
int a;
pragma(msg, typeof((int b) => b * 2)); // int function(int b) pure
nothrow @nogc @safe
pragma(msg, typeof(() => a * 2)); // int delegate() pure nothrow
@nogc @safe
}
A question to ask is, why do you need it?
-Steve
