Re: [stack] disallowing recursive definitions

William Tanksley scripsit:

> I don't know the term "lambda-lift", and Google knows of it mainly as
> a bunch of source files (I did find a 1985 paper on the topic, but
> it's a little dense to answer my questions easily). My question: does
> that include code copying -- in other words, is it possible for a
> single stretch of code-text in the original GOTO program to be present
> in two places in the lambda-lifted code text?

No, it doesn't.  Lambda-lifting is a transformation of an inner (nested)
procedure into a top-level procedure by adding one argument for each
variable that is free in the inner procedure but bound in some enclosing
procedure.  All calls are transformed likewise.

For example:

	(lambda (x y) ... (lambda (z w) ... x ...) ...)

lambda-lifts to:

	(lambda (z-of-x w x) ... x ...)
	(lambda (x y) ... (z-of-x w x) ...)

so z is renamed to z-of-x (or in some other way) and goes from one
argument to two.

This will not work, or at least requires extra machinery, when z is
passed out of x to be called from somewhere else.  But that is not the
case for lambdas made out of tagbody labels.

-- 
John Cowan    [email protected]    http://ccil.org/~cowan
        Sound change operates regularly to produce irregularities;
        analogy operates irregularly to produce regularities.
                --E.H. Sturtevant, ca. 1945, probably at Yale