#1245: Turn tuples into syntactic sugar for heterogeneous lists
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Reporter: [EMAIL PROTECTED] | Owner:
Type: feature request | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.6
Severity: normal | Keywords:
Difficulty: Unknown | Testcase:
Architecture: Unknown | Os: Unknown
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It would be nice if (x,y,z) were syntactic sugar for a
[http://homepages.cwi.nl/~ralf/HList/ heterogeneous list], i.e. (x :*: y
:*: z :*: HNil) where
{{{
data a :*: b = a :*: b
data HNil = HNil
}}}
(:*: associating to the right). Using functional dependencies and the
techniques from the HList paper, we could then process tuples of arbitrary
length in a uniform matter: for example, the Data.Monoid.Monoid instances
for tuples. At the same time, this would create a slightly more light-
weight syntax for heterogeneous lists, making them more acceptable for use
cases like functions with optional or keyword arguments.
I'm not sure how much existing code would this would break. Showing and
reading heterogeneous lists as tuples doesn't seem hard to implement. I
don't know about Typeable and friends.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1245>
GHC <http://www.haskell.org/ghc/>
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