In some respects, there’s another path: further generalizing overloaded
lists with the right machinery for list syntax to support hlists and sized
lists!
I prototyped out a possible type class for this that predates pattern
synonyms and I believe it could be made even nicer with pattern synonyms
https://github.com/cartazio/HetList/blob/master/HetList.hs
Here’s the example code above!
On Thu, Jan 13, 2022 at 8:06 PM Viktor Dukhovni
On Thu, Jan 13, 2022 at 07:50:02PM -0500, Jeffrey Brown wrote:
You can get very close -- specifically, to within two extra characters -- to the brevity you're imagining without introducing any new extensions:
data Foo = Foo Int Int deriving (Show)
f :: (Int, Int) -> Foo f = uncurry Foo
g :: Int -> Int -> Foo g = Foo
{-# LANGUAGE PatternSynonyms #-}
pattern F :: Int -> Int -> Foo pattern F f s = Foo f s
Which abbreviates a frequently used constructor, and works in pattern matches too.
λ> case F 4 "2" of { F x y -> show x ++ y } "42"
But the original question is really about logical completeness of overloading primitives, not about work-arounds, so bottom line I too don't think that overloading tuples is justified, since this breaks extensibility if constructor type signatures later become ambiguous, I don't think the idea has sufficient merit.
-- Viktor. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.