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From: Nils M Holm <news2...@t3x.org>
Newsgroups: comp.lang.lisp
Subject: Re: bignums in clisp
Date: 3 Oct 2012 12:24:00 GMT
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References: <7c6cd833-2c5b-43a4-9825-7fd540ece54a@googlegroups.com> <87627jgmta.fsf@gnu.org> <k44gnl$o33$1@news.ox.ac.uk> <barmar-ABCFBE.16040128092012@news.eternal-september.org> <20120928140653.318@kylheku.com> <barmar-4DCE69.21544929092012@news.eternal-september.org> <k4ev7v$gp7$1@news.ox.ac.uk> <k4f0j3$r38$1@reader1.panix.com> <87obkkvr1e.fsf@kuiper.lan.informatimago.com> <k4g5gg$ftb$1@reader1.panix.com> <k4h12a$7t7$1@news.ox.ac.uk> <871uhfvlra.fsf@kuiper.lan.informatimago.com>
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Pascal J. Bourguignon <p...@informatimago.com> wrote:
> (defun ?      (x y) (expt x y))
> (defun ??    (x y) (expt x (expt y y)))
> (defun ???  (x y) (expt x (expt y (expt y y))))
> (defun ???? (x y) (expt x (expt y (expt y (expt y y)))))

If you get tired of inventing ????'s (sorry, only ASCII here), notice
that the operator can be generalized for more then 4 ?'s as:

(f (- n 1) x (f n x (- y 1)))

where F is the function implementing the operators and N is the order
of the operator (number of ?'s). See also: hyper operator.

Here's an implementation in Scheme: http://t3x.org/s9fes/hyper.scm.html

-- 
Nils M Holm  < n m h @ t 3 x . o r g >  www.t3x.org