anchor.diff:  
   WHILE: 'WHILE';
   
  -INTEGER: ('+' | '-')? [1-9][0-9]*;
  +INTEGER: [1-9]([0-9]*);
   
  -ID: [a-zA-Z][a-z0-9A-Z_]*;
  +ID: [a-zA-Z] ([a-z0-9A-Z_]*);
   
   STRINGLITERAL: '"' .*? '"';
   
  
positive.code: 
  while_statement: WHILE '(' expression ')' statement;
  
  expression: (variable (exprop variable)*) | simple_expression;
  
  exprop: '=' | '-+' | '*=' | '/=' | '+=';
  
  
negative.code: or_expression:
  	unary_relationexpression ('&&' unary_relationexpression)*;
  
  unary_relationexpression: '!'? relation_expression;
  
  relation_expression: add_expression (relop add_expression)*;
  
  relop: '<=' | '>=' | '==' | '!=' | '>' | '>';
  
  