Re: [Haskell-cafe] Implicit newtype unwrapping

Hi, Am Donnerstag, den 03.12.2009, 13:03 -0500 schrieb David Menendez:

On Thu, Dec 3, 2009 at 6:28 AM, Joachim Breitner wrote:

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Am Donnerstag, den 03.12.2009, 11:13 +0000 schrieb Matthew Pocock:

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Perhaps what you are looking for is a more powerful "defining" semantics?

newtype MyFoo = Foo defining (Foo(..)) -- all class instances that Foo has are delegated through from MyFoo

it goes into the right direction, but I’d also like to have this also capeable to derive single functions (giving them a new name), and not only class instances.

Something like the restricted type synonym extension in Hugs?

http://cvs.haskell.org/Hugs/pages/users_guide/restricted-synonyms.html

yes, this is very close to what I’d hope for. Last minor (but really minor) wish: I don’t think it would hurt to allow the use of this feature independent of the definition of the newtype: I could have a newtype Foo = Foo Int somewhere, possibly in a different module, and write something like myFoo :: Foo -> (Foo,Foo) resolving Foo myFoo a = (a,a+a) (syntax and wording very ad hoc and not thought through). But yes, I think I’d be happy to have hugs’ extension here at hand sometimes. Greetings, Joachim -- Joachim Breitner e-Mail: mail@joachim-breitner.de Homepage: http://www.joachim-breitner.de ICQ#: 74513189 Jabber-ID: nomeata@joachim-breitner.de