// 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);
}
public Unit VisitWhileStmt(Stmt.While stmt)
{
Resolve(stmt.Condition);
Resolve(stmt.Body);
return(Unit.Default);
}
private Stmt ForStatement()
{
Consume(LEFT_PAREN, "Expect '(' after 'while'");
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);
}
object Stmt.IVisitor <object> .VisitWhileStmt(Stmt.While stmt)
{
Resolve(stmt.condition);
Resolve(stmt.body);
return(null);
}