Haskell Language List Literals

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GHC's OverloadedLists extension allows you to construct list-like data structures with the list literal syntax.

This allows you to Data.Map like this:

> :set -XOverloadedLists
> import qualified Data.Map as M
> M.lookup "foo" [("foo", 1), ("bar", 2)]
Just 1

Instead of this (note the use of the extra M.fromList):

> import Data.Map as M
> M.lookup "foo" (M.fromList [("foo", 1), ("bar", 2)])
Just 1