[Haskell-cafe] Re: Suggestion: Syntactic sugar for Maps!
bulat.ziganshin:
Hello circ,
Thursday, November 27, 2008, 9:59:08 PM, you wrote:
So why not {hello: 1, there: 2} ?
mymap hello:1 there:2
where mymap implementation is left to the reader :)
Hey, well, even easier:
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleInstances #-}
import Data.Map
import Data.String
import Text.JSON
instance IsString (Map Int Bool) where
fromString = fromList . read
-- or, say, JSON syntax for assoc lists.
{-
fromString s = case resultToEither (decode s) of
Right a - a
Left s - error s
-}
test :: Map Int Bool
test = [(7, True), (1, False)]
main = print test
-- Don
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Re: [Haskell-cafe] Re: Suggestion: Syntactic sugar for Maps!
In all fairness, this basically forces you to say trust me to the compiler for something that should be verifiable statically. A typo results in a runtime error -- in a way, this is worse than Perl. Quasi-quotes are really the right answer but hardly simple in this case... -- _jsn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Suggestion: Syntactic sugar for Maps!
Don Stewart wrote:
bulat.ziganshin:
Hello circ,
Thursday, November 27, 2008, 9:59:08 PM, you wrote:
So why not {hello: 1, there: 2} ?
mymap hello:1 there:2
where mymap implementation is left to the reader :)
I can't see the context of the beginning of this thread, but I've always
found:
fromList [(hello,1),(there,2)]
to be a relatively simple syntax, and still checked at compile time.
Anonymous sum + product types plus lists are a pretty good approximation
for lots of concrete syntax, and they're type checks.
(Anonymous sum, Either, is slightly more syntactically heavy than you'd
like, though...)
Jules
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Re: [Haskell-cafe] Re: Suggestion: Syntactic sugar for Maps!
On Fri, Nov 28, 2008 at 12:04 AM, Jules Bean [EMAIL PROTECTED] wrote: I can't see the context of the beginning of this thread, but I've always found: fromList [(hello,1),(there,2)] to be a relatively simple syntax, and still checked at compile time. I never liked that. Too much syntax overhead. But this clears it right up: foo = fromList [ hello : 1, there : 2 ] where (:) = (,) And also I haven't been following the thread, so this may not be any kind of answer. Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
