🚀 go-pugleaf

dorai@cs.rice.edu (Dorai Sitaram) writes:
>I don't understand the big pain in the neck part.  Is it the notion of
>lexical scope in itself, or is it the way to get it in Object Logo
>that is a big pain?

Lexical scope itself.  Or perhaps I should say, the incompatibility of
lexical scope with other aspects of Logo.  I think lexical scope is fine
in Scheme, for example, where it combines with first-class functions and
a heavy use of macros so that you can do anything you want to do.

In Logo, without first-class functions, it's common to use "first-class
expressions" to achieve the same goal.  That is, if you want to write a
higher-order function like MAP, what you pass as an argument is a list
containing an expression, which then gets RUN repeatedly by MAP.  That
expression must have access to the local variables of whatever procedure
called MAP.

Object Logo does provide ways to get dynamic scope by asking for it
explicitly, but that means that the Object Logo user has to have a pretty
sophisticated understanding of scope rules to know when to ask.  (And to
be fair, part of my annoyance is that until quite recently the feature
about asking for dynamic scope didn't really work!)

I could go on for a while but we had a discussion of this in the
newsgroup not long ago so maybe we should continue by mail if you
want to pursue it.