class Token:
	# Represents the single smallest unit that makes up an expression.
	
	def __init__(self, value, type, is_negative_variable = False):
		self.value = value
		self.type = type
		self.is_negative_variable = is_negative_variable
		
	def __str__(self):
		return "Value: %s" %(self.value)

class TokenType:
	add = 0
	subtract = 1
	multiply = 2
	divide = 3
	power = 4
	variable = 5
	constant = 6
	exp_start = 7
	exp_end = 8
	unknown = 9

	OPERATOR_VERBS = {
		0 : "Adding",
		1 : "Subtracting",
		2 : "Multiplying",
		3 : "Dividing",
		4 : "Raising"
	}
	
	TOKEN_NAMES = {
		0 : "Addition",
		1 : "Subtraction",
		2 : "Multiplication",
		3 : "Division",
		4 : "Power",
		5 : "Variable",
		6 : "Constant",
		7 : "Expression Start",
		8 : "Expression End",
		9 : "Unknown"
	}

	OPERATORS = {
		'+' : add,
		'-' : subtract,
		'*' : multiply,
		'^' : power,
		'/' : divide
	}

	@staticmethod
	def get_operator_verb(token):
		# Returns the verb that corresponds to the supplied Token object's value field, or
		# throws an error if the Token object isn't a mathmatical operator.
		if not token in TokenType.OPERATOR_VERBS:
			raise ValueError("An operator verb could not be found.", "token")
		return TokenType.OPERATOR_VERBS[token]

	@staticmethod
	def get_operator(character):
        # Accepts an individual character and returns either the mathmatical operator TokenType or unknown.
		if not character in TokenType.OPERATORS:
			return TokenType.unknown
		return TokenType.OPERATORS[character]
	
	@staticmethod
	def get_token_type_name(tokenType):
		# Returns the token's full name based on the TokenType value.
		return TokenType.TOKEN_NAMES[tokenType]