I have often wanted to use a guard in a lambda function and had thought it wasn't possible. But apparently the case construct allows a viable approach. Here is a silly example.

testCase = map

(\xs -> case xs of

[] -> "empty list"

[y] | y < 5 -> "small singleton"

| otherwise -> "large singleton"

_ -> "multi-element list")

> testCase [[], [2], [7], [1,2,3]]

["empty","small singleton","large singleton","multi-element list"]

It seems particularly useful to be able to include both patterns and guards in case expressions. I haven't seen this usage anywhere. Is it considered bad form?

-- Russ