[99p]SynChecker

import Data.Char

----- predefined test expressions
syn1 = "this-is-a-long-identifier"
syn2 = "this-ends-in-"
syn3 = "two--hyphens"

----- the syntax checker
synTail :: String -> Bool
synTail [] = True
synTail (x:xs) = if (x == '-') then (synChecker' xs) else (synChecker' (x:xs))
                 where synChecker' :: String -> Bool
                       synChecker' [] = False
                       synChecker' xs = isAlphaNum (head xs) && synTail (tail xs)
synChecker :: String -> Bool
synChecker [] = True
synChecker xs = isAlpha(head xs) && synTail (tail xs)