gistfile1.hs

rotateR :: [a] -> [a]
rotateR [x] = [x]
rotateR xs = last xs : init xs

-- Make a pattern to match the consonants and vowels in a word where a cons is
-- not "aeiou" or y preceded by a cons e.g., "happy" -> ("happy", "cvccv")
wordDesc :: String -> (String, String)
wordDesc str =
    (str, [corv (a,b,i) | (a,b,i) <- zip3 str (rotateR str) [0..len]])
    where len = length str - 1
          corv (a,b,i)
            | a == 'y' && i /= 0 && b `notElem` vs = 'v'
            | a `elem` vs = 'v'
            | otherwise = 'c'
            where vs = "aeiou"

-- Measure the number of consonant sequences in the word in the form
-- [c]vcvc[v] == 2 where the inner 'vc' sequences are counted.
measure :: (String, String) -> Int
measure (_,ds) =
    length $ filter (=='c') ds'
    where ds' = dropWhile (=='c') [head a | a <- group ds]

-- Tests if our word or stem ends with a given character
endswith :: (String, String) -> Char -> Bool
endswith (str,_) c = c == last str

-- Tests if our word or stem contains a vowel
hasvowel :: (String, String) -> Bool
hasvowel (_,ds) = 'v' `elem` ds

-- Tests if our word or stem ends with a double consonant
endsdblc :: (String, String) -> Bool
endsdblc (str,ds) =
    last ds == 'c' && (last $ init str) == last str

-- Tests if our word or stem ends with the pattern 'cvc' and does
-- not end with the characters 'x', 'w' or 'y'
endscvc :: (String, String) -> Bool
endscvc (str,ds) =
    drop (length ds - 3) ds == "cvc" && last str `notElem` "xwy"