-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Am 07/21/2013 03:08 PM, schrieb Mateusz Kowalczyk:
On 21/07/13 13:36, martin wrote:
Hello all,
What is the best way to enter several (key, value) pairs into a Map, such that the code "looks nice", kind of like the do-notation with monads.
I suppose this question is not really specific to a Map. It is about chaining functions with a type of a1 ->...-> an -> b -> b.
Is there any syntactic sugar available?
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There's no sugar but that doesn't mean you have to have something that doesn't look nice! Hackage tells me it's an instance of monoid.
*Main Data.Monoid Data.Map> singleton 1 2 fromList [(1,2)] *Main Data.Monoid Data.Map> singleton 1 2 <> singleton 2 3 fromList [(1,2),(2,3)] *Main Data.Monoid Data.Map> singleton 1 2 <> singleton 2 3 <> singleton 4 3 fromList [(1,2),(2,3),(4,3)]
There's of course fromList *Main Data.Monoid Data.Map> fromList [(1, 2), (3, 4)] <> fromList [(7, 2), (8, 4)] fromList [(1,2),(3,4),(7,2),(8,4)]
*Main Data.Monoid Data.Map> fromList $ zip [1 .. 3] ['a' .. 'z'] fromList [(1,'a'),(2,'b'),(3,'c')]
I don't think that fromList looks nice enough, especially considering that you can split it across many lines etc. It'd be easier to help if you could be more specific about what you're looking for.
I just want to insert several key/value pairs, something like Map.empty insert key1 val1 insert key2 val2 return theMap I know I can achieve this with dollars and by reversing the order, such that Map.empty is at the end. But I don't think it is pretty. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlHr7u4ACgkQKkUHbleEZGW2DgCgmInJcFCcRCNpW/rdvq1X5Q8W NJwAnA7SjDs+nGxOv77VZblb7Zge+d0x =0G+B -----END PGP SIGNATURE-----