Check if 2 strings are cycles

gistfile1.hs

rotate :: [Char] -> [Char] -> Int -> Bool
rotate _ _ 0 = False
rotate s1 s2 len = if s1' == s2 then True else rotate s1' s2 (len-1)
    where s1' = tail s1 ++ [head s1]
cyclep :: [Char] -> [Char] -> Bool
cyclep str1 str2 = rotate str1 str2 (length str1)