Re: Re: [stack] Re: Programming Puzzle
"Christopher Diggins" <[email protected]>
| Newsgroups | gmane.comp.lang.concatenative |
|---|---|
| Message-ID | <[email protected]> |
On 5/18/07, Brent L Kerby <[email protected]> wrote: > > > Unless, I am mistaken I believe "dup i" or "recurse" is the classical Y > combinator. > > "dup i" is indeed a useful component in building the y combinator, although they are not the same. The difference is this: > > [P] dup i == [P] P > [P] y == [[P] y] P > > "dup i" is the concatenative equivalent of the classical combinator M (= \f. ff), the combinator which applies its operand to itself. Ah yes! Thank you for the correction. > Manfred has offered a simpler concatenative "y" combinator (at http://www.latrobe.edu.au/philosophy/phimvt/joy/j05cmp.html, in the section "The fixpoint theorem and the y combinator") I notice he calls "M" "x". > Sorry, I've gone off on a bit of a tangent; I just think this is quite an interesting result that's worth mentioning again. As always I enjoy your posts and insights Brent. - Christopher