In defence of the two-namespace rule

[Phil Jensen]

Edward Welbourne <eddyw at lsl.co.uk> wrote, inter alia:

> Define a function, foo, which returns a function it has defined, as bar,
> during its suite; have bar refer to some of the local variables of foo.
> With lexical scoping, the interpreter is obliged to keep the namespace
> foo used (on that invocation) for as long as anyone retains a reference
> to what it returned.

I'm newish enough not to know to what extent the lexical scoping
advocates regard closures as crucial.  From a language-design
standpoint the two issues are separable, however.  For example,
the (lexically-scoped) Modula-3 reference says:

  | A local procedure can be passed as a parameter but not
  | assigned, since in a stack implementation a local procedure
  | becomes invalid when the frame for the procedure containing
  | it is popped.

Personally, I agree with Edward (and many others) that the two-scope
rule harmonizes well with Python.  Lexical scoping seems to play
better in a language with declarations.

  Phil