type Tab = [String]

task :: Tab -> Tab
task t =
    let (receiveTab t)      = a
        (receivePosition t) = b --receivePosition and nextPosition are not really relevant to the context of this question
    in nextPosition a b

receiveTab :: Tab -> Tab
receiveTab (h:t)
        | elem ' ' h = []
        | otherwise  = receiveTab t

task2.hs: Parse error in pattern: receiveTab