code: public AEqualsBinaryExp readDefEqualsExpression() throws ParserException,
  			LexException
  	{
  		// This is an oddball parse for the "def" expression :-)
  
  		PExp exp = readEvaluatorP1Expression();
  		LexToken token = lastToken();
  
  		if (readToken().is(VDMToken.EQUALS))
  		{
  			return AstFactory.newAEqualsBinaryExp(exp, token, readEvaluatorP1Expression());
  		}
  
  		throwMessage(2029, "Expecting <set bind> = <expression>");
  		return null;
  	}
docs: Relations Family...