[Python-Dev] A Hygienic Macro System in Python?

2002年3月20日 12:21:54 +1200 (NZST)

Paul Prescod <paul@prescod.net>:
> Me:
>> > except that the thunk would have to have write access to
> > the namespace it's embedded in, perhaps implemented by
> > sharing the stack frame.
>> If the idea is for it to be a macro feature then yes. But it could be
> JUST an anonymous implicit thunk. Isn't that how it is in Ruby or
> Smalltalk?

The idea was to mimic both the syntax and semantics of built-in
control structures as closely as possible. If the body were a normal
2.2-style nested scope, the semantics would be different. Most other
languages that allow passing of closures don't have this problem,
because their closures do have write access to outer scopes.
> How would the procedure know what variable names to expect in the
> block?

Not sure what problem you're seeing here. The body would be compiled
as an integral part of the procedure scope it's embedded in, just like
the body of any built-in control structure. Names assigned to in the
body would become local variables of the procedure.
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	 | A citizen of NewZealandCorp, a	 |
Christchurch, New Zealand	 | wholly-owned subsidiary of USA Inc. |
greg@cosc.canterbury.ac.nz	 +--------------------------------------+