Re: 8 queens problem in Oforth

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.forth
Subject	Re: 8 queens problem in Oforth
Date	2015-03-23 15:32 -0700
Organization	A noiseless patient Spider
Message-ID	<87619r8hw1.fsf@jester.gateway.sonic.net> (permalink)
References	(16 earlier) <menl66$ade$1@dont-email.me> <87pp808se2.fsf@jester.gateway.sonic.net> <menqmi$q1t$1@dont-email.me> <87lhio8iai.fsf@jester.gateway.sonic.net> <mepcfl$m0l$1@dont-email.me>

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Bernd Paysan <bernd.paysan@gmx.de> writes:
> You probably wouldn't want to create a derivative function...
> : derivative ( f1 h xt -- f2 )  >r
>   ftuck fover f+ r@ execute fswap r> execute f- fswap f/ ;

Sure, this is fine in the Newton step for finding a zero of f, but
suppose then want find the minimum or maximum of f?  You'd like use the
exact same Newton step subroutine to find a zero of the derivative.
E.g.  to find the x that minimizes x**2 - 4x + 5 you could use something
along the lines of
    minimize f = solve (derivative f)
    x1 = minimize (\x -> x**2 - 4x + 5)

This didn't take much thought because the thing that came back from
derivative is a re-usable, first class function.  And there's surely
some approach possible to deal with that too, but it's sure nice to not
have to spend your coding time figuring out such things, if the compiler
can do it for you.

> But certainly, you could
> : derivative { h xt -- xt' }
>   :noname postpone fdup h fliteral postpone f+ xt compile,
>   postpone fswap xt compile, postpone f- h fliteral postpone f/ postpone ; ;
> You then would most likely use that derivative function at compile
> time, not at run-time.

Right, not that great for creating lots of them on the fly, since they
aren't gc'd.

Have you looked at John Hughes' paper "Why functional programming
matters"?

http://www.cse.chalmers.se/~rjmh/Papers/whyfp.pdf

The section with numerical derivative examples starts on page 11, and
then it goes on to numerical integration and is pretty interesting.  It
develops an integration function in a quite natural way that's much
better than the ones usually taught in math class.  Of course the
resulting algorithm could be back-ported into Forth or Fortran (it may
be the same as the traditional Romberg method), but it's much more
natural using the higher-order approach.

Thread

8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-19 07:53 +0000
  Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-19 08:58 -0700
    Re: 8 queens problem in Oforth Doug Hoffman <glidedog@gmail.com> - 2015-03-20 08:16 -0400
      Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-21 10:11 +0000
        Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-21 03:45 -0700
          Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-21 14:14 -0700
            Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-21 14:28 -0700
              Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-21 14:38 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-21 15:15 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-21 18:23 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-22 03:03 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 14:04 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-22 16:34 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 21:49 -0700
                Re: 8 queens problem in Oforth Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-03-23 00:05 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-23 21:43 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-24 04:13 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-23 00:17 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-21 19:47 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-22 08:41 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 13:37 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-22 18:13 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 13:55 -0700
                Re: 8 queens problem in Oforth "Alex McDonald" <blog@rivadpm.com> - 2015-03-22 21:08 +0000
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 14:39 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 14:50 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-22 22:58 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 15:13 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 01:03 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 17:33 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 02:37 +0100
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 20:53 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 21:11 -0700
                Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-23 11:34 +0000
                Re: 8 queens problem in Oforth albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-23 19:31 +0000
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 15:56 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-24 00:38 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 19:08 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-30 05:02 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-30 05:08 -0700
                Re: 8 queens problem in Oforth "Alex McDonald" <blog@rivadpm.com> - 2015-03-30 15:36 +0100
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 16:46 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 15:32 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 23:48 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 16:14 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 17:54 -0700
                Re: 8 queens problem in Oforth "Alex McDonald" <blog@rivadpm.com> - 2015-03-22 23:09 +0000
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-22 22:11 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 14:48 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 15:11 -0700
                Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-23 11:29 +0000
                Re: 8 queens problem in Oforth albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-23 12:20 +0000
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 14:21 -0700
                Re: 8 queens problem in Oforth Coos Haak <chforth@hccnet.nl> - 2015-03-22 22:30 +0100
            Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-23 14:45 +0000
              Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 14:53 -0700
                Re: 8 queens problem in Oforth "Elizabeth D. Rather" <erather@forth.com> - 2015-03-24 09:16 -1000
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-24 12:40 -0700
                Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-30 12:24 +0000
          Re: 8 queens problem in Oforth Coos Haak <chforth@hccnet.nl> - 2015-03-21 22:27 +0100
  Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-19 20:31 +0000
  Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-19 20:35 +0000
  Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-21 17:31 +0000
    Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-21 20:50 +0000
    Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-21 21:52 +0000

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