On Mon, 18 Oct 2010 15:20:39 -0400, Tomek Sowiński <j...@ask.me> wrote:
Dnia 18-10-2010 o 20:53:15 Steven Schveighoffer <schvei...@yahoo.com>
napisał(a):
On Mon, 18 Oct 2010 14:31:26 -0400, Tomek Sowiński <j...@ask.me> wrote:
Initializing immutable structures is a source of constant grief.
Anything non-trivial requires instancing a mutable structure,
initializing it, and then either casting to immutable (it's up to you
to ensure no alias leaked) or, not to violate the type system,
duplicate the whole.
Aren't we supposed to get so-called immutable constructors?
Haven't heard, can you point to the discussion?
I think it's in TDPL, don't have a copy so I'm not sure how to refer you.
I know the really really old pdf document that talks about the future
direction of D2 had them.
Anyway, if these immutable ctors are defined inside the type, then the
library writer may not provide a ctor suitable for your case (very
possible).
Yes true. However with your method, it's also very possible they don't
provide a pure ctor.
I think an immutable ctor has different restrictions. In light of the new
version of pure, perhaps your idea could obviate the need for immutable
constructors. In other words, a pure constructor just got a *lot* easier
to write, and almost all ctors should be pure. If that's the case, then
many would be 'immutably pure' since they take only value types.
Plus, if the thing I wrote is correct, why not?
Not saying it's not correct, it sounds correct to me, but I think we need
to verify we aren't creating too many ways to do the same thing here
(which may even mean immutable constructors are redundant).
If that's not what you mean, can you give an example of such grief?
Build an immutable dictionary that would hold the program's options.
This particular problem should be solvable by changing the type of all
literals to immutable :)
I think at some point, we need something like you propose -- where given
the properties of a function, you can implicitly convert its return value
to immutable. This makes things much easier to deal with.
-Steve
