6.2.13. Lambda-case¶

LambdaCase¶

Since:	7.6.1

Allow the use of lambda-case syntax.

The LambdaCase extension enables expressions of the form

\case { p1 -> e1; ...; pN -> eN }

which is equivalent to

\freshName -> case freshName of { p1 -> e1; ...; pN -> eN }

Note that \case starts a layout, so you can write

\case
  p1 -> e1
  ...
  pN -> eN

Additionally, since GHC 9.0.1, combining LambdaCase with Arrows allows \case syntax to be used as a command in proc notation:

proc x -> (f -< x) `catchA` \case
  p1 -> cmd1
  ...
  pN -> cmdN