public object VisitClassStmt(Class stmt)
{
Environment.Define(stmt.Name.Lexeme, null);
Dictionary <String, CoxFunction> methods = new Dictionary <String, CoxFunction>();
Object superclass = null;
if (stmt.Superclass != null)
{
superclass = Evaluate(stmt.Superclass);
if (!(superclass is CoxClass))
{
throw new RuntimeError(stmt.Name, "Superclass must be a class.");
}
Environment = new Environment(Environment);
Environment.Define("super", superclass);
}
foreach (Function method in stmt.Methods)
{
CoxFunction function = new CoxFunction(method, Environment, method.Name.Lexeme.Equals("init"));
methods.Add(method.Name.Lexeme, function);
}
CoxClass klass = new CoxClass(stmt.Name.Lexeme, (CoxClass)superclass, methods);
if (superclass != null)
{
Environment = Environment.Enclosing;
}
Environment.Assign(stmt.Name, klass);
return(null);
}
public CoxFunction FindMethod(CoxInstance instance, String name)
{
CoxClass klass = this;
while (klass != null)
{
if (klass.Methods.ContainsKey(name))
{
return(klass.Methods[name].Bind(instance));
}
klass = klass.Superclass;
}
return(null);
}
public object VisitSuperExpr(Super expr)
{
int distance = Locals[expr];
CoxClass superclass = (CoxClass)Environment.GetAt(distance, "super");
// "this" is always one level nearer than "super"'s environment.
CoxInstance receiver = (CoxInstance)Environment.GetAt(distance - 1, "this");
CoxFunction method = superclass.FindMethod(receiver, expr.Method.Lexeme);
if (method == null)
{
throw new RuntimeError(expr.Method, $"Undefined property '{expr.Method.Lexeme}'.");
}
return(method);
}
public CoxClass(String name, CoxClass superclass, Dictionary <String, CoxFunction> methods)
{
Name = name;
Superclass = superclass;
Methods = methods;
}
public CoxInstance(CoxClass klass)
{
Klass = klass;
}