gistfile1.hs

--
-- split bstr into 3 parts: before, on, and after first line with match
--
fgrep_line pat bstr =
    if BS.null bstr
    then (BS.empty, BS.empty, BS.empty)
    else (head, BS.concat[left, right], rem)
        where
        (h, t)       = breakOn pat bstr
        left         = BS.tail $ afterLast (pack "\n") h
        (right, rem) = breakOn (pack "\n") t
        head         = dropLast (BS.length left + 1) h