private Stmt ForStatement()
{
Consume(LEFT_PAREN, "Expect '(' after 'for'.");
// For loop doesn't get its own statement.
// Instead we desugar and reduce it to a while loop.
Stmt initializer;
if (Match(SEMICOLON))
{
initializer = null;
}
else if (Match(VAR))
{
initializer = VarDeclaration();
}
else
{
initializer = ExpressionStatement();
}
Expr condition = null;
if (!IsCurrentTokenType(SEMICOLON))
{
condition = Expression();
}
Consume(SEMICOLON, "Expect ';' after loop condition.");
Expr increment = null;
if (!IsCurrentTokenType(RIGHT_PAREN))
{
increment = Expression();
}
Consume(RIGHT_PAREN, "Expect ')' after for clauses.");
// Parse the statement body of the for loop.
Stmt body = Statement();
if (increment != null)
{
// Add increment to be executed after the main body.
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)
{
// Run the initializer once before the while loop.
body = new Stmt.Block(new List <Stmt> {
initializer, body
});
}
return(body);
}
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>
{
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);
}
public object VisitWhileStmt(Stmt.While stmt)
{
Resolve(stmt.condition);
Resolve(stmt.body);
return(null);
}
public Void VisitWhileStmt(Stmt.While stmt)
{
Resolve(stmt.Condition);
Resolve(stmt.Body);
return(null);
}
public string VisitWhileStmt(Stmt.While stmt)
{
throw new NotImplementedException();
}
public string VisitWhileStmt(Stmt.While stmt) => throw new System.NotImplementedException();
private Stmt ForStatement()
{
Consume(LEFT_PAREN, "Expect '(' after 'for'.");
Stmt initializer;
if (Match(SEMICOLON))
{
initializer = null;
}
else if (Match(VAR))
{
initializer = VarDeclaration();
}
else
{
initializer = ExpressionStatement();
}
Expr condition = null;
if (!Check(SEMICOLON))
{
condition = Expression();
}
Consume(SEMICOLON, "Expect ';' after loop condition.");
Expr increment = null;
if (!Check(RIGHT_PAREN))
{
increment = Expression();
}
Consume(RIGHT_PAREN, "Expect ')' after for clauses.");
var body = Statement();
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);
}