Re: [stack] disallowing recursive definitions

Thanks for the examples.

I think there's a relation between stack languages and Lisp's anaphoric
macros:

 http://www.bookshelf.jp/texi/onlisp/onlisp_15.html#SEC99 -and-
 http://common-lisp.net/project/anaphora/anaphora.html

In a stack language, the top of the stack is the anaphoric "it".


On Thu, Feb 28, 2008 at 6:43 PM, John Nowak wrote:

>
> On Feb 28, 2008, at 6:47 PM, Joe Bowbeer wrote:
>
> > As a former Schemer and fan of continuations, I'm conditioned to
> > view (tail)
> > recursion as the simpler, more powerful concept.  Not looping.
>
> I have a Scheme background as well.
>
> > Functional programming languages rely on recursion and still boast of
> > referential transparency: the ability to substitute function
> > applications by
> > their definitions.  But they don't take the substitution as far as
> > you'd
> > like to...
>
> Indeed.
>
> > Functional languages favor recursion over looping because looping
> > traditionally requires a loop variable whose value changes: a side
> > effect.
>
> What's surprising is how easily the stack lets you write code in an
> imperative style while remaining purely functional. Here's a small
> example where, given a natural number, we construct a list from 1 to
> that number:
>
>    ; Scheme, via recursion
>
>    (define (foo n)
>      (let f ((n n) (xs '()))
>        (if (zero? n)
>            xs
>            (f (- n 1) (cons n xs)))))
>
>    ; Joy-like, via recursive combinator
>
>    foo = null swap ((cons) keep pred) (zero?) until pop
>
>    ; Another Joy-like version
>    ; (prec :: A int int (A int -> A) -> A)
>
>    foo = null swap 1 (cons) prec
>
> - John
>
>


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