On Wed, 17 Dec 2008 00:39:00 +0100, Robert Jacques <[email protected]>
wrote:
On Tue, 16 Dec 2008 12:28:43 -0800, Simen Kjaeraas
<[email protected]> wrote:
So this does not seem pure to you?
int myPureFunction(int x) {
return x;
}
Short answer: That's a function, not a delegate and without a 'pure' tag
it's unreasonable for the complier to know it's logically pure.
I agree with this, but feel that's beside the point argued by mastrost.
My point (and I believe mastrost's as well) was that the above function
and mastrost's example could be considered pure by the simple addition
of the 'pure' keyword.
Long answer: Your original arguement was:
But the fact is that when returning a delegate, its closure freezes
forever and so
behaves like a local variable and not like a global variable by respect
to the
delegate :
Which I read to mean that a returned delegate is inherently pure. On a
second read, I think you mean that the closure heap variables may be
treated as immutable once a delegate is returned if the delegate doesn't
mutate them. While an interesting observation, it too is easily broken:
Ah, I read it to mean that a delegate with no side effects is just as
pure as a function with none, which I find hard to argue against. As D
is a systems language, one might argue that casting a delegate to pure
is reasonable, as it may be too hard to statically check if it is pure,
and a cast is a confirmation from the programmer that yes, he knows
what he's doing.
--
Simen
