[Compiler-sig] Assign nodes

[Finn Bock]

[Jeremy]

>>>>>> "FB" == Finn Bock <bckfnn@worldonline.dk> writes:
>
>  FB> And I don't like this change one single bit. Yes sure, it looks
>  FB> prettier than using Lvalue and it captures useful information,
>  FB> but it makes a one-pass AST builder a lot harder to do.
>
>I felt it simplified the code generator for the compiler package, but
>I don't have any experience with a one-pass AST builder.  So it's hard
>for me to judge what the tradeoffs are.  You haven't written a code
>generator, right?

No, not from scratch. I did add the augassign code to both our bytecode
generator and our javacode generator and so I do appreciate the benefit
of being able to tell an evaluate Slice node from an assignment Slice
node (and from a delete Slice node and from a AugAssign Slice node).

>If so, we've each got experience with one end of
>the problem, but not with both.
>
>  FB> You probably don't care because you have an intermediate parse
>  FB> tree with all the context needed to know if you must create a
>  FB> Name node or a AssignName node.
>
>I'd be interested in taking a look at the one-pass AST builder.
>Eventually, I'd like to have one for CPython.  
>
>  FB> When my parser detect a name, I have no way of knowing if an
>  FB> equal sign will turn up later. So I'll have to pick one node
>  FB> type (like Name) and rebuild that part of the tree later if it
>  FB> turned out that it was part of an assignment or deletion. Ugly.
>
>Indeed, and perhaps a compelling case against the richer AST.  I
>assume the difference is that CPython's compiler is top-down and yours
>is bottom-up?

Yes, jjtree creates the AST bottom-up.

>  FB> As I have said before, I think the desire for correct typing in
>  FB> the tree is overrated and I would rather remove the 'assign' sum
>  FB> altogether and add a flag to the Attribute, Subscript, Name,
>  FB> List and Tuple nodes that captured the use of the node (like
>  FB> 'Get', 'Set' and 'Del').
>
>I'll noodle with the code generator in the compiler package and see
>what it would look like if the AssignXXX nodes went away.

Don't forget the flag!

I prefer the flag (instead of seperate classes) because it is a lot
easier and faster to change an int in the sub-tree than it is to
recreate the sub-tree with different classes.

Lets not get too hung up on it, I can also implement it with AssignXXXX
(and DeleteXXXX and AugAssignXXXX) nodes.

regards,
finn