"Serge D. Mechveliani" <mech...@botik.ru> writes: | On Tue, Feb 14, 2012 at 02:54:17AM -0600, Gabriel Dos Reis wrote: | > "Serge D. Mechveliani" <mech...@botik.ru> writes: | > | > | In Spad, rc.foo | > | | > | selects a field named foo in a record rc. | > | In Haskell, this is | > | foo rc -- similar as applying any function. | > | | > | Indeed, foo has type Record(foo : Foo, ...) -> Foo. | > | In particular, it allows, for example, | > | map foo (records :: List Record(...)). | > | > Haskell does not really have first class records, Haskell' folks are | > agonizing over how to properly define records in Haskell and what to do | > with the dot notation. See the various record and dot proposals and | > ongoing discussion on Haskell' list. | > | > http://hackage.haskell.org/trac/ghc/wiki/Records/DotOperator | > [..] | | | 1. I think, it has quite good records. For example, | | -------------------------------------------------- | data Gauss r = Gauss {real :: r, im :: r} | -- a record | | -- '::' means ':' of Spad. | -- `r' a parameter, which can be viewed as say IntegralDomain. | | testL = [g, g {im = 2}, g {im = 3}] -- a list of three "G-numbers" | where | g = Gauss {real = 0, im = 1} :: Gauss Int | -------------------------------------------------- | | Then: (im (head testL)) + 3 --> 4, | map im testL --> [1, 2, 3] | | Why do you say that it does not really have first class records?
because, all the above lets you do is to name a particular field of a particular data type. It does not allow you to use the same name for the field of a completely different data type. | 2. As I understand, the current Haskel discussion on records is of | _how to develop the denotations further_, to an even better state. | Because the Haskell conflict is only between good and even better :-) I think that misses the fundamental point of the current discussion in the Haskell community. | | For example, the next problem is the field name overloading. | For example, how to allow 'im' to appear in different records, and its | type to be found correctly. Inventing various kinds of a sugar. | I never followed the whole discussion. | But in principle, g.im still can be converted by the compiler to (im g), | there are possible various denotations. | | My aim was only to point at the idea. I understood that. I was just pointing out that Spad's situation is a bit ahead of that of Haskell on this specific point. -- Gaby ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ open-axiom-devel mailing list open-axiom-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/open-axiom-devel
