[Compiler-sig] More jython progress.

[Finn Bock]

Hi,

I now got a version of jythonc running with the new AST. As always
jythonc (the java sourcecode generator) is about twice as complicated as
the java bytecode generator. Sigh.

In jythonc, Jim Hugunin had added an additional abstraction layer on top
of the anonymous SimpleNode ast tree that jython have used so far. With
the new AST we no longer need the abstraction layer. Without that layer
the code in jythonc became (IMO) a lot simpler and easier to follow. The
new AST also means that the codegen in our two generators are far more
similar than before. A huge win because we always have to implement new
language features in both generators. IOW I'm very happy with the new 
AST and with the use of asdl as a way of describing the AST. Good work 
Jeremy.

Since jythonc is written in python I would like to work towards an
agreement on what the public python API to the AST should be like.

What package/module should contain the AST node classes?

In jython we have a scope analyzer that analyze a module and return
symboltables for module, class and function levels. I guess CPython must
also have some such thing. Should the compiler package have a public API
to such scope analyzer?

Similar we have future analyzer. Should we define a public API to this?

What should be the public names of the AST node classes? I have used the
name of the Constructors directly but I had to change the name of the 
'except' production (to 'excepthandler').

Each field in a constructor is obviously a class instance attribute.

Each asdl constructor becomes a java class. That means new attributes 
can't be added dynamicly. A strong limitation compared to a python class 
instance. It also means that the __XXX__ attributes can't be changed or 
depended on (such as __class__ and __name__).

The sequences in the asdl becomes java arrays. That means that the 
elements in a sequence can be changed but the length of the sequence 
can't. I think we should ban all attempts to modify the sequences.


Are these restrictions unacceptabe for the potential users of the AST 
tree? I would like to reach some type of agreement soon.

regards,
finn