Re: [stack] disallowing recursive definitions

William Tanksley, Jr scripsit:

> I'm generally on Knuth's side on this one.

Remember that Knuth thought Dijkstra was *mostly* right, and takes care to
disclaim the notion that he is in favor of random gotos.  AFAIK, gotos are
only used in TeX to compensate for Pascal's lack of a return statement.

> But I don't see how tail recursion is a general goto statement. It
> seems structured -- in particular, a tail recursion has only one entry
> point.

If you take an arbitrary tagbody (a list of statements and labels with
gotos embedded in the statements), you can restructure it into a sequence
of functions, one per label, where each function ends by tail calling the
next function in sequence (corresponding to flowing through the label)
and each goto is changed into a tail call.  This can be done entirely as
a local transformation.

So while it's true that tail calls have only one entry point, entry
points and labels are basically the same thing from a Scheme perspective,
something that neither Knuth nor Dijkstra deals with.  "Lambda: the
ultimate GOTO."

-- 
Well, I have news for our current leaders       John Cowan
and the leaders of tomorrow: the Bill of        [email protected]
Rights is not a frivolous luxury, in force      http://www.ccil.org/~cowan
only during times of peace and prosperity.
We don't just push it to the side when the going gets tough.  --Molly Ivins