From lliao@ren.eecis.udel.edu Sun Nov 17 23:38:04 2002
Date: Sun, 17 Nov 2002 23:37:34 -0500 (EST)
From: Li Liao <lliao@ren.eecis.udel.edu>
Subject: Re: hw4



>
> I have couple of questions about hw#4.
>
> for the subclass, the assignment sheet said that a class is  considered  a
> subclass of itself. Does this mean that if I do
> 	val CInfo (super_id1, vdecls, mdict) = lookup cid1 ctab
> 	val CInfo (super_id2, vdecls, mdict) = lookup cid2 ctab
> (if I can say this)
> then, super_id1 == super_id2 ?

It means that if cid1 == cid2 then subclass cid1 cid2 should return true.

>
> For the (Field (e, f)), I am not sure about the datatype of Field of "Expr
> * Id" I think that Id seems to be the name of the field.

That is correct.

> Then, what is the Expr which is not null infront of Id?

Expr should evaluate to an object whose ftab should contain
the f.

> I can assume that it could be "This." But once again I am not sure.

Expr certainly can evalute to "This", but can be any object depending
on the program that is being interpreted.

>
> For task 3, I understand that when e1, e2 are the Int, we should compare
> wether they are same as in i=3, j=3 and i==j?. When e1, e2 are objects,
> saying List l1 and List l2 then we have to find out wether they are same
> object?

Please refer to message 26 on the bboard.

> How can we know e1, e2 are Int or Object? Can I think of them as Varcecl
> and get the Type?

Do pattern matching.


I hope this is helpful.

Li