2009/11/5 Sebastiaan Visser sfvis...@cs.uu.nl:
Hello all,
Wouldn't it be nice if we could write point free case statements?
I regularly find myself writing down something like this:
myFunc = anotherFunc $ \x - case x of
Left err - print err
Right msg - putStrLn msg
We could really use a case statement in which we skip the scrutinee and make
`(case of {})' be syntactic sugar for `(\x - case x of {})'.
So we could write:
myFunc = anotherFunc $ case of
Left err - print err
Right msg - putStrLn msg
A minor syntactical addition, a big win!
Cheers,
--
Sebastiaan Visser
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Morten Rhiger implemented Type-safe pattern combinators [1], which
are essentially a library for pattern matching, entirely within
Haskell98. As an example, he implemented anonymous pattern-matching
with this library, which is similar to what you ask for. It would be
certainly be possible to implement your proposal with his library.
My library first-class-patterns [2] on Hackage essentially follows
Morten Rhiger's approach, but makes the types more understandable. I
implemented point free case expressions (the 'elim' function) and
monadic pattern matches (the 'mmatch' function) in version 0.2.0,
which I just uploaded. For instance, you could write
import Data.Pattern
anonymous matching
ex6 :: Show a = Either a String - IO ()
ex6 = elim $
left var - print
| right var - putStrLn
-- monadic matching
ex8 :: IO ()
ex8 = mmatch getLine $
cst - return ()
| var- putStrLn . (You said ++)
Cheers,
Reiner
[1] http://www.itu.dk/people/mir/typesafepatterns.pdf
[2] http://hackage.haskell.org/package/first-class-patterns
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
