anchor.diff:  	
   //literals
   literal
  -	:	IntegerLiteral			# IntegerLiteral
  -	|	FloatingPointLiteral	# FloatingPointLiteral
  +	:	FloatingPointLiteral
  +	|	IntegerLiteral
   	;
   
   /*
  
positive.code: // Integer literals
  IntegerLiteral
  	:	'0'
  	|	Sign? NonZeroDigit Digits*
  	;
  
  FloatingPointLiteral
  	:	Sign? Digits '.' Digits?
  	;
  
  fragment
  
negative.code: 	|	literal						# LiteralExpression
  	|	Identifier			        # IdentifierExpression
  	|	expression Operator=(INC|DEC)		# PostIncDecExpression
  	|	Operator=(
  			SUB
  		|	BANG
  		)
  		expression	# UnaryExpression
  	|	expression
  		Operator=(
  			MUL 
  		|	DIV
  		|	MOD
  