instance Show RegExp where

	showsPrec _ Epsilon		= showChar '@'
	showsPrec _ (Literal c)
		| isSymbol c		= showChar '\''
					. showChar c
					. showChar '\''
		| otherwise		= showChar c
	showsPrec n (Star e)		= showsPrec 10 e . showChar '*'
	showsPrec n (OneOrMore e)	= showParen (n == 4)
					$ showsPrec 10 e
					. showChar '+'
	showsPrec _ (Optional e)	= showsPrec 10 e
					. showChar '?'
	showsPrec n (e1 `Or` e2)	= showParen (n /= 0 && n /= 4)
					$ showsPrec 4 e1
					. showChar '+'
					. showsPrec 4 e2
	showsPrec n (e1 `Then` e2)	= showParen (n /= 0 && n /= 6)
					$ showsPrec 6 e1
					. showChar ' '
					. showsPrec 6 e2