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");
Stmt body = Statement();
if (increment != null)
{
body = new Stmt.Block(new List <Stmt>(new[] { 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>(new[] { initializer, body }));
}
return(body);
}
public string VisitLiteral(Expr.Literal expr)
{
if (expr.Value == null)
{
return("nil");
}
if (expr.Value is string)
{
return(string.Format("\"{0}\"", expr.Value));
}
return(expr.Value.ToString());
}
// varDecl :: "var" IDENTIFIER ( "=" expression )? ";" ;
private Stmt VarDeclaration()
{
var name = Consume(TokenType.Identifier, "Expect variable name");
Expr init = new Expr.Literal(null);
if (MatchAny(TokenType.Equal))
{
init = Expression();
}
Consume(TokenType.Semicolon, "Expect ';' after variable declaration");
return(new Stmt.Var(name, init));
}
public object VisitLiteralExpr(Expr.Literal expr)
{
return(expr.Value);
}
// forStmt :: "for" "(" ( varDecl | exprStmt | "; ")
// expression? ";"
// expression? ")" statement ;
private Stmt ForStatement()
{
Consume(TokenType.LeftParen, "Expect '(' after 'for'");
// Get the initializer.
Stmt init;
if (MatchAny(TokenType.Semicolon))
{
init = null;
}
else if (MatchAny(TokenType.Var))
{
init = VarDeclaration();
}
else
{
init = ExpressionStatement();
}
// Get the condition.
Expr condition = null;
if (!Check(TokenType.Semicolon))
{
condition = Expression();
}
Consume(TokenType.Semicolon, "Expect ';' after loop condition");
// Get the increment.
Expr increment = null;
if (!Check(TokenType.RightParen))
{
increment = Expression();
}
Consume(TokenType.RightParen, "Expect ')' after for clauses");
var body = Statement();
// Desugar by creating a while loop instead.
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 (init != null)
{
body = new Stmt.Block(
new List <Stmt> {
init,
body
});
}
return(body);
}
object Expr.IVisitor <object> .VisitLiteralExpr(Expr.Literal expr)
{
return(expr.value);
}
public object VisitLiteralExpr(Expr.Literal expr)
{
return(null);
}
public Unit VisitLiteral(Expr.Literal expr)
{
return(Unit.Default);
}
public Void Visit(Expr.Literal expr)
{
return(Void.Instance);
}
object Expr.IVisitor <object> .VisitLiteralExpr(Expr.Literal expr)
{
return(null);
}