6.2.14. 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