示例#1
0
文件: Parser.cs 项目: sisakat/cslox
        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.");

            loopCount++;
            Stmt body = Statement();

            loopCount--;

            if (increment != null)
            {
                body = new Stmt.Block(new List <Stmt>()
                {
                    body,
                    new Stmt.Expression(increment)
                });
            }

            if (condition == null)
            {
                condition = new Expr.Literal(true);
            }
            body = new Stmt.While(condition, body);

            if (initializer != null)
            {
                body = new Stmt.Block(new List <Stmt>()
                {
                    initializer,
                    body
                });
            }

            return(body);
        }