class A
	attributes
		att1 : Integer
		att2 : Integer
		list : Sequence(A)
	operations
		  operationname1() = self.att1 + self.att2 < 3
		  operationname2()
			 pre namepre: self.att1 <= self.att2
			 post  namepost: self.list-> notEmpty()
end

OperationsBase:
	'operations'
		(operations+=OperationType)*;

OperationType:
	OperationComplex | OperationQuery;

OperationQuery:
	operationDeclaration=OperationDeclaration '=' operationbody=OCLExpression (conditions+=ConditionType)*;

OperationComplex:
	operationDeclaration=OperationDeclaration (conditions+=ConditionType)*;

OperationDeclaration:
	name=ID '()';
	
ConditionType:
	Precondition | Postcondition;

Precondition:
	'pre' (name=ID)? ':' oclexpression=OCLExpression;
	
Postcondition:
	'post' (name=ID)? ':' oclexpression=OCLExpression;

language = StandardLanguage {
	..
	parserGenerator = {
  		options = {
    		          backtrack = true
  		}
	}
}

/**
 * RetokenizingTokenSource accomodates backtracking limitations in the ANTRL lexer when used from Xtext.
 *
 * The problem is the three overlapping syntaxes
 * INT.INT leading to a Floating Point lteral
 * INT..INT leading to a Collection range
 * INT.ID leading to a numeric navigation
 *
 * ANTLR proceeds to INT. but won't backup when the character after the . is bad.
 *
 * The code here allows the basic lexer to be ignorant of floating point syntax so that it correctly parses
 * INT.INT as INT DOT INT
 * INT..INT as INT DOTDOT INT
 * INT.INTe+INT as INT DOT INT ID PLUS INT
 * so the code here recognises the floating point literal and reconsttructs. As an additional benefit 'e' and 'E' are not keywords.
 */