Ejemplo n.º 1
0
        private Stmt ForStatement()
        {
            Consume(TokenType.LEFT_PAREN, "Expect '(' after 'for'.");

            Stmt initializer;

            if (Match(TokenType.SEMICOLON))
            {
                initializer = null;
            }
            else if (Match(TokenType.VAR))
            {
                initializer = VarDeclaration();
            }
            else
            {
                initializer = ExpressionStatement();
            }

            Expr condition = null;

            if (!Check(TokenType.SEMICOLON))
            {
                condition = Expression();
            }
            Consume(TokenType.SEMICOLON, "Expect ';' after loop condition.");

            Expr increment = null;

            if (!Check(TokenType.RIGHT_PAREN))
            {
                increment = Expression();
            }
            Consume(TokenType.RIGHT_PAREN, "Expect ')' after for clauses.");

            // This is the for loop body provided by the user
            Stmt forLoopBody = Statement();

            //////////////// The for loop is rewritten as a while loop. ///////////
            //Copy for loop body into a list of while loop statements
            List <Stmt> whileLoopStatements = new List <Stmt> {
                forLoopBody
            };

            //If an increment was given, append it to the list of while loop statements
            if (increment != null)
            {
                whileLoopStatements.Add(new Stmt.Expression(increment));
            }

            //Form the while loop, without the initializer
            //Condition is forced to "true" if the for loop had no condition expression
            Stmt whileLoop = new Stmt.While(
                condition ?? new Expr.Literal(true),
                new Stmt.Block(whileLoopStatements)
                );

            //If no initializer given, just return the while loop.
            //Otherwise, insert the initializer just above the while loop
            return(initializer == null ? whileLoop : new Stmt.Block(new List <Stmt>
            {
                initializer,
                whileLoop,
            }));
        }
 public MyVoid VisitWhileStmt(Stmt.While stmt)
 {
     resolve(stmt.condition);
     resolve(stmt.body);
     return(null);
 }