Haskell Language Common GHC Language Extensions LambdaCase
Example
A syntactic extension that lets you write \case in place of \arg -> case arg of.
Consider the following function definition:
dayOfTheWeek :: Int -> String
dayOfTheWeek 0 = "Sunday"
dayOfTheWeek 1 = "Monday"
dayOfTheWeek 2 = "Tuesday"
dayOfTheWeek 3 = "Wednesday"
dayOfTheWeek 4 = "Thursday"
dayOfTheWeek 5 = "Friday"
dayOfTheWeek 6 = "Saturday"
If you want to avoid repeating the function name, you might write something like:
dayOfTheWeek :: Int -> String
dayOfTheWeek i = case i of
0 -> "Sunday"
1 -> "Monday"
2 -> "Tuesday"
3 -> "Wednesday"
4 -> "Thursday"
5 -> "Friday"
6 -> "Saturday"
Using the LambdaCase extension, you can write that as a function expression, without having to name the argument:
{-# LANGUAGE LambdaCase #-}
dayOfTheWeek :: Int -> String
dayOfTheWeek = \case
0 -> "Sunday"
1 -> "Monday"
2 -> "Tuesday"
3 -> "Wednesday"
4 -> "Thursday"
5 -> "Friday"
6 -> "Saturday"
