Re: on Perl

On 2024-04-17, John Ames <commodorejohn@gmail.com> wrote:

On Wed, 17 Apr 2024 21:52:06 +0200
David Brown <david.brown@hesbynett.no> wrote:
>

I think that when finding the definition of a word, Forth just
searches back through the stack of definitions until it gets a hit.
And if that word definition uses other non-primitive words, it goes
backwards from where it currently is, looking only at definitions
from before the current word was defined.  Is that right?  And if so,
can you do "forward declarations", and mutual recursion somehow?

>
That's my understanding, yes; essentially, it's a consequence of the
fact that definitions are stored as a list of pointers, and re-
definitions are simply appended to the dictionary without going back
through the rest of it to update any pointers to the prior definition.
A strange design choice, but they're consistent with it.

I don't know at all whether Forth does this or not, but this design
choice allows the list to be restored to a prior state, whereby the
recent definitions are forgotten, and the old ones revealed again,
similarly to shadowed lexicals being revealed again upon the terminaton
of an inner scope.

It sounds reminiscent of the assoc list representation of the lexical
environment in a rudimentary Lisp interpreter.

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