Lambda case

The LambdaCase GHC extension introduces a kind of expression that is something of a cross between a case expression and a lambda expression. A lambda case expression is written using the \case keyword, which does not exist in standard Haskell.

When we have a combination of a lambda and a case expression that looks like this:

we can rewrite slightly more tersely as a lambda-case, like this:

LambdaCase has been in GHCGHC documentation for LambdaCase since version 7.6.1.