public string Visit(Expr.Literal literal)
{
string ret = "nil";
if (literal.value != null)
{
ret = literal.value.ToString();
}
return(ret);
}
private Expr Primary()
{
Expr expr = null;
if (Match(TokenType.False))
{
expr = new Expr.Literal(false);
}
else if (Match(TokenType.True))
{
expr = new Expr.Literal(true);
}
else if (Match(TokenType.Nil))
{
expr = new Expr.Literal(null);
}
else if (Match(TokenType.Number, TokenType.String))
{
expr = new Expr.Literal(Previous().literal);
}
else if (Match(TokenType.Super))
{
Token keyword = Previous();
Consume(TokenType.Dot, "Expect '.' after 'super'.");
Token method = Consume(TokenType.Identifier, "Expect superclass method name.");
expr = new Expr.Super(keyword, method);
}
else if (Match(TokenType.This))
{
expr = new Expr.This(Previous());
}
else if (Match(TokenType.Identifier))
{
expr = new Expr.Variable(Previous());
}
else if (Match(TokenType.LeftParen))
{
expr = Expression();
Consume(TokenType.RightParen, "Expect ')' after expression.");
expr = new Expr.Grouping(expr);
}
else
{
throw Error(Peek(), "Expect expression.");
}
return(expr);
}
public object Visit(Expr.Literal expr)
{
return(expr.value);
}
private Stmt ForStatement()
{
Consume(TokenType.LeftParen, "Expect '(' after 'for'");
// initializer
Stmt initializer = null;
if (Match(TokenType.Semicolon))
{
initializer = null;
}
else if (Match(TokenType.Var))
{
initializer = VarDeclaration();
}
else
{
initializer = ExpressionStatement();
}
// condition
Expr condition = null;
if (!Check(TokenType.Semicolon))
{
condition = Expression();
}
Consume(TokenType.Semicolon, "Expect ';' after loop condition.");
// increment
Expr increment = null;
if (!Check(TokenType.RightParen))
{
increment = Expression();
}
Consume(TokenType.RightParen, "Expect ')' after for clauses.");
// body
Stmt body = Statement();
// desugar
if (increment != null)
{
List <Stmt> statements = new List <Stmt>();
statements.Add(body);
statements.Add(new Stmt.Expression(increment));
body = new Stmt.Block(statements);
}
if (condition == null)
{
condition = new Expr.Literal(true);
}
body = new Stmt.While(condition, body);
if (initializer != null)
{
List <Stmt> statements = new List <Stmt>();
statements.Add(initializer);
statements.Add(body);
body = new Stmt.Block(statements);
}
return(body);
}
public object Visit(Expr.Literal expr)
{
return(null); // do nothing
}
