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English Idiom in Unix: Directory Recursively

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  English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-17 15:26 -0700
    Re: English Idiom in Unix: Directory Recursively Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-17 17:20 -0600
      Re: English Idiom in Unix: Directory Recursively "Martin P. Hellwig" <martin.hellwig@gmail.com> - 2011-05-18 22:22 +0000
    Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-18 09:42 +1000
    Re: English Idiom in Unix: Directory Recursively "Steven W. Orr" <steveo@syslang.net> - 2011-05-17 21:16 -0400
    Re: English Idiom in Unix: Directory Recursively Roland Hutchinson <my.spamtrap@verizon.net> - 2011-05-18 04:51 +0000
      Re: English Idiom in Unix: Directory Recursively "Pascal J. Bourguignon" <pjb@informatimago.com> - 2011-05-18 07:19 +0200
        Re: English Idiom in Unix: Directory Recursively tar@sevak.isi.edu (Thomas A. Russ) - 2011-05-17 23:42 -0700
          Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-18 09:26 +0100
            Re: English Idiom in Unix: Directory Recursively tar@sevak.isi.edu (Thomas A. Russ) - 2011-05-18 09:16 -0700
              Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-18 19:11 +0100
                Re: English Idiom in Unix: Directory Recursively Raymond Wiker <raw@RAWMBP-2.local> - 2011-05-18 20:20 +0200
                  Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-18 19:39 +0100
                    Re: English Idiom in Unix: Directory Recursively Raymond Wiker <raw@RAWMBP-2.local> - 2011-05-18 21:09 +0200
                      Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-18 21:02 +0100
                        Re: English Idiom in Unix: Directory Recursively Raymond Wiker <raw@RAWMBP-2.local> - 2011-05-18 22:40 +0200
                          Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-19 05:56 +0100
                    Re: English Idiom in Unix: Directory Recursively tar@sevak.isi.edu (Thomas A. Russ) - 2011-05-19 16:14 -0700
                  Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-19 04:41 +1000
              Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-19 04:12 +1000
              Re: English Idiom in Unix: Directory Recursively "Pascal J. Bourguignon" <pjb@informatimago.com> - 2011-05-18 20:57 +0200
                Re: English Idiom in Unix: Directory Recursively tar@sevak.isi.edu (Thomas A. Russ) - 2011-05-19 16:17 -0700
                  Re: English Idiom in Unix: Directory Recursively "Pascal J. Bourguignon" <pjb@informatimago.com> - 2011-05-20 02:38 +0200
                    Re: English Idiom in Unix: Directory Recursively Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2011-05-20 12:00 +0300
          Re: English Idiom in Unix: Directory Recursively Peter Moylan <invalid@peter.pmoylan.org.invalid> - 2011-05-18 22:09 +1000
            Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-18 06:14 -0700
              Re: English Idiom in Unix: Directory Recursively Peter Moylan <invalid@peter.pmoylan.org.invalid> - 2011-05-19 11:06 +1000
                Re: English Idiom in Unix: Directory Recursively Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.COM> - 2011-05-21 09:32 +0100
                  Re: English Idiom in Unix: Directory Recursively Lars Enderin <lars.enderin@telia.com> - 2011-05-21 11:52 +0200
                    Re: English Idiom in Unix: Directory Recursively Lars Enderin <lars.enderin@telia.com> - 2011-05-21 11:54 +0200
                      Re: English Idiom in Unix: Directory Recursively Lars Enderin <lars.enderin@telia.com> - 2011-05-21 11:56 +0200
                Re: English Idiom in Unix: Directory Recursively Grant Edwards <invalid@invalid.invalid> - 2011-05-21 15:34 +0000
        Re: English Idiom in Unix: Directory Recursively Roland Hutchinson <my.spamtrap@verizon.net> - 2011-05-20 06:50 +0000
      Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-17 23:06 -0700
        Re: English Idiom in Unix: Directory Recursively Harrison Hill <harrishill@gmx.com> - 2011-05-17 23:50 -0700
          Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-18 00:16 -0700
          Re: English Idiom in Unix: Directory Recursively Peter Moylan <invalid@peter.pmoylan.org.invalid> - 2011-05-18 22:19 +1000
            Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 13:16 -0700
              Re: English Idiom in Unix: Directory Recursively Peter Moylan <invalid@peter.pmoylan.org.invalid> - 2011-05-30 22:58 +1000
          Re: English Idiom in Unix: Directory Recursively see@sig.for.address (Victor Eijkhout) - 2011-05-18 12:59 -0500
            Re: English Idiom in Unix: Directory Recursively Roland Hutchinson <my.spamtrap@verizon.net> - 2011-05-20 06:54 +0000
              Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-20 17:10 +1000
            Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 13:28 -0700
              Re: English Idiom in Unix: Directory Recursively Peter Moylan <invalid@peter.pmoylan.org.invalid> - 2011-05-30 23:02 +1000
            Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 13:28 -0700
          Re: English Idiom in Unix: Directory Recursively Glenn Knickerbocker <NotR@bestweb.net> - 2011-05-18 16:54 -0400
        Re: English Idiom in Unix: Directory Recursively Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-18 00:58 -0600
          Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-18 00:10 -0700
            Re: English Idiom in Unix: Directory Recursively Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-18 08:32 -0600
              Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-18 08:15 -0700
                Re: English Idiom in Unix: Directory Recursively Ian Kelly <ian.g.kelly@gmail.com> - 2011-05-18 09:43 -0600
    Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-18 09:12 +0100
      Re: English Idiom in Unix: Directory Recursively Espen Vestre <espen@vestre.net> - 2011-05-18 10:20 +0200
      Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-19 23:21 +0200
        Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-20 05:28 +0100
          Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-23 20:48 +0200
        Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-19 22:13 -0700
          Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-20 06:55 +0000
            Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-20 09:48 +0100
              Re: English Idiom in Unix: Directory Recursively rusi <rustompmody@gmail.com> - 2011-05-20 10:21 -0700
            Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-23 20:56 +0200
              Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-24 00:18 +0000
                Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-25 00:06 +0200
                  Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-25 10:40 +1000
                    Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 14:18 -0700
                    Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 14:19 -0700
                  Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-24 23:05 -0700
                  Re: English Idiom in Unix: Directory Recursively Thorsten Kampe <thorsten@thorstenkampe.de> - 2011-05-25 09:26 +0200
                    Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-25 00:51 -0700
                      Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-25 17:59 +1000
                    Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-25 21:59 +0000
                      Re: English Idiom in Unix: Directory Recursively Thorsten Kampe <thorsten@thorstenkampe.de> - 2011-05-26 10:48 +0200
                        Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-26 10:06 +0000
                          Re: English Idiom in Unix: Directory Recursively Thorsten Kampe <thorsten@thorstenkampe.de> - 2011-05-26 12:46 +0200
                      Re: English Idiom in Unix: Directory Recursively harrismh777 <harrismh777@charter.net> - 2011-05-27 09:31 -0500
                  Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-25 22:58 +0000
                    Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-26 14:00 +1000
                    Re: English Idiom in Unix: Directory Recursively Thorsten Kampe <thorsten@thorstenkampe.de> - 2011-05-26 10:59 +0200
                      Re: English Idiom in Unix: Directory Recursively "Charles" <C.Sanders@DeleteThis.Bom.GOV.AU> - 2011-05-26 20:58 +1000
                        Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-26 21:12 +1000
                          Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 14:38 -0700
                            Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-30 07:46 +1000
                              Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 15:54 -0700
                          Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 14:38 -0700
                        Re: English Idiom in Unix: Directory Recursively Thorsten Kampe <thorsten@thorstenkampe.de> - 2011-05-26 13:20 +0200
                          Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-26 21:28 +1000
                          Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-26 14:51 -0700
                    Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-28 21:36 +0200
                      Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-29 05:58 +1000
                        Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-29 00:49 +0000
                        Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-30 23:04 +0200
                          Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-30 23:17 +0000
                      Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-29 07:28 +1000
                        Re: English Idiom in Unix: Directory Recursively Rikishi42 <skunkworks@rikishi42.net> - 2011-05-30 23:10 +0200
                  Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 13:58 -0700
                    Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-30 07:27 +1000
            Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 13:39 -0700
    Re: English Idiom in Unix: Directory Recursively Mike Barnes <mikebarnes@bluebottle.com> - 2011-05-18 10:25 +0100
      Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-18 13:00 -0700
        Re: English Idiom in Unix: Directory Recursively Hans Georg Schaathun <hg@schaathun.net> - 2011-05-18 21:19 +0100
          Re: English Idiom in Unix: Directory Recursively Lanarcam <lanarcam1@yahoo.fr> - 2011-05-18 22:33 +0200
        Re: English Idiom in Unix: Directory Recursively Mike Barnes <mikebarnes@bluebottle.com> - 2011-05-18 22:00 +0100
        Re: English Idiom in Unix: Directory Recursively Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.COM> - 2011-05-20 08:10 +0100
          Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-22 13:22 -0700
            Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-23 08:46 +1000
              Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-22 16:17 -0700
                Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-23 09:32 +1000
                  Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-23 21:20 -0700
                    Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-24 14:28 +1000
                      Re: English Idiom in Unix: Directory Recursively Xah Lee <xahlee@gmail.com> - 2011-05-24 10:40 -0700
                        Re: English Idiom in Unix: Directory Recursively Chris Angelico <rosuav@gmail.com> - 2011-05-25 08:14 +1000
                          Re: English Idiom in Unix: Directory Recursively Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-05-25 10:15 +0000
        Re: English Idiom in Unix: Directory Recursively rantingrick <rantingrick@gmail.com> - 2011-05-29 13:32 -0700
      Re: English Idiom in Unix: Directory Recursively Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.COM> - 2011-05-20 08:07 +0100
    Re: English Idiom in Unix: Directory Recursively John Nagle <nagle@animats.com> - 2011-05-18 13:07 -0700
    Re: English Idiom in Unix: Directory Recursively Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.COM> - 2011-05-20 08:00 +0100
      Re: English Idiom in Unix: Directory Recursively David Schwartz <davids@webmaster.com> - 2011-05-27 22:56 -0700

Page 3 of 6 — ← Prev page 1 2 [3] 4 5 6  Next page →

#5824

On Wed, 18 May 2011 12:59:45 -0500, Victor Eijkhout wrote:

> Harrison Hill <harrishill@gmx.com> wrote:
> 
>> No need - I have the Dictionary definition of recursion here:
>> 
>> Recursion: (N). See recursion.
> 
> If you tell a joke, you have to tell it right.
> 
> Recursion: (N). See recursion. See also tail recursion.

Very good!

-- 
Roland Hutchinson		

He calls himself "the Garden State's leading violist da gamba,"
... comparable to being ruler of an exceptionally small duchy.
--Newark (NJ) Star Ledger  ( http://tinyurl.com/RolandIsNJ ) 

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#5833

On Wed, 18 May 2011 12:59:45 -0500, Victor Eijkhout wrote:
> Recursion: (N). See recursion. See also tail recursion.

caching proxy (n): If you already know what recursion is, this is the
same. Otherwise, see recursion.

ChrisA

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#6571

On May 18, 12:59 pm, s...@sig.for.address (Victor Eijkhout) wrote:
> Harrison Hill <harrish...@gmx.com> wrote:
> > No need - I have the Dictionary definition of recursion here:
>
> > Recursion: (N). See recursion.
>
> If you tell a joke, you have to tell it right.

Jeez, speaking of bad colloquialisms...

 """if you're going to "share" a joke you should at least "recite" it
CORRECTLY."""

Thank you.

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#6656

rantingrick wrote:
> On May 18, 12:59 pm, s...@sig.for.address (Victor Eijkhout) wrote:
>> Harrison Hill <harrish...@gmx.com> wrote:
>>> No need - I have the Dictionary definition of recursion here:
>>> Recursion: (N). See recursion.
>> If you tell a joke, you have to tell it right.
> 
> Jeez, speaking of bad colloquialisms...
> 
>  """if you're going to "share" a joke you should at least "recite" it
> CORRECTLY."""

He was her man
But he was doing her incorrectly.

I'm not convinced that this new meaning of "share" has contributed
anything of value to the language.  Which is possibly why people stopped
using it in about the 1980s.

-- 
Peter Moylan, Newcastle, NSW, Australia.      http://www.pmoylan.org
For an e-mail address, see my web page.

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#6572

On May 18, 12:59 pm, s...@sig.for.address (Victor Eijkhout) wrote:
> Harrison Hill <harrish...@gmx.com> wrote:
> > No need - I have the Dictionary definition of recursion here:
>
> > Recursion: (N). See recursion.
>
> If you tell a joke, you have to tell it right.

Jeez, speaking of bad colloquialisms...

 """if you're going to "share" a joke you should at least "recite" it
CORRECTLY."""

Thank you.

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#5740

On 05/18/2011 02:50 AM, Harrison Hill wrote:
> Recursion: (N). See recursion.

The index of IBM's Document Composition Facility SCRIPT/VS Text
Programmer's Guide, Release 3.0 (form SH35-0069-2), put it thus:

> Circular definition
>     See definition, circular
> definition
>     circular  211
>         See also circular definition

Sadly, only the Release 4 manuals are available online anymore.

¬R

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#5663

On Wed, May 18, 2011 at 12:06 AM, rusi <rustompmody@gmail.com> wrote:
> 4. Recursion in 'recursion theory' aka 'computability theory' is
> somehow different from recursion in programming.

Um, it is.  Consider the simple function (lambda x, y: x + y).
Mathematically, this function is recursive.  Algorithmically, it is
not.  Do you disagree?

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#5665

On May 18, 11:58 am, Ian Kelly <ian.g.ke...@gmail.com> wrote:
> On Wed, May 18, 2011 at 12:06 AM, rusi <rustompm...@gmail.com> wrote:
> > 4. Recursion in 'recursion theory' aka 'computability theory' is
> > somehow different from recursion in programming.
>
> Um, it is.  Consider the simple function (lambda x, y: x + y).
> Mathematically, this function is recursive.  Algorithmically, it is
> not.  Do you disagree?

See the definition of primitive recursion eg.

http://en.wikipedia.org/wiki/Primitive_recursive_function#Definition

(2 of the second set of "more complex" definitions) from where the
name 'primitive recursion' is presumably derived)

And for the more general (wider) class of 'recursive' functions (in
the math sense aka computable functions) see a little below:

http://en.wikipedia.org/wiki/Primitive_recursive_function#Relationship_to_recursive_functions

Of course I grant that the adjective 'recursive' is used differently
in computability and in programming but the roots are not all that
different.

If I remember right (I may be misremembering) Hofstader, referring to
the invention of 'recursive function' by Godel, says something to the
effect that Godel was inventing lisp 30 years before lisp...

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#5700

On Wed, May 18, 2011 at 1:10 AM, rusi <rustompmody@gmail.com> wrote:
>> Um, it is.  Consider the simple function (lambda x, y: x + y).
>> Mathematically, this function is recursive.  Algorithmically, it is
>> not.  Do you disagree?
>
> See the definition of primitive recursion eg.
>
> http://en.wikipedia.org/wiki/Primitive_recursive_function#Definition
>
> (2 of the second set of "more complex" definitions) from where the
> name 'primitive recursion' is presumably derived)
>
> And for the more general (wider) class of 'recursive' functions (in
> the math sense aka computable functions) see a little below:
>
> http://en.wikipedia.org/wiki/Primitive_recursive_function#Relationship_to_recursive_functions

I know what primitive recursive and computable functions are, thanks.
What you're failing to explain is why you would consider that function
to be recursive from a programming standpoint.  In programming, when
we say a function is recursive, we mean that it is implemented using
the technique of recursion, not that it is computable.  Since we're
throwing around Wikipedia links, see the definition in the first
sentence at:

http://en.wikipedia.org/wiki/Recursion_%28computer_science%29

In fact, the mathematical definition would not be useful for
programming since to us a function is an implementation of an
algorithm (I expect Lispers may quibble over this, but it is true even
there).  Thus, in programming, all functions are computable.

> Of course I grant that the adjective 'recursive' is used differently
> in computability and in programming but the roots are not all that
> different.

Not just the adjective 'recursive', but also the noun 'function'.  I'm
not sure of the exact etymology of 'recursive', although I would bet
that the mathematical usage came first and the programming usage is a
derivative of it.

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#5702

On May 18, 7:32 pm, Ian Kelly <ian.g.ke...@gmail.com> wrote:
> On Wed, May 18, 2011 at 1:10 AM, rusi <rustompm...@gmail.com> wrote:
> >> Um, it is.  Consider the simple function (lambda x, y: x + y).
> >> Mathematically, this function is recursive.  Algorithmically, it is
> >> not.  Do you disagree?
>
> > See the definition of primitive recursion eg.
>
> >http://en.wikipedia.org/wiki/Primitive_recursive_function#Definition
>
> > (2 of the second set of "more complex" definitions) from where the
> > name 'primitive recursion' is presumably derived)
>
> > And for the more general (wider) class of 'recursive' functions (in
> > the math sense aka computable functions) see a little below:
>
> >http://en.wikipedia.org/wiki/Primitive_recursive_function#Relationshi...
>
> I know what primitive recursive and computable functions are, thanks.

Myself, my memory of things studied badly decades ago may be
fuzzy :D )

Anyhow taking those links to be authoritative, what I am saying is:
Coming from the computability side, there are 3 related but distinct
definitions of recursive:

1. Anything computable is recursive  -- general recursive or partial
recursive
  (evidently there is some dispute re these definitions
  http://mathworld.wolfram.com/RecursiveFunction.html
2. Primitive recursive -- ie any function that is defined using
 - constant
 - successor
 - projection
 - composition
 - primitive recursion
[This definition is recursive in a bad sense but let that be... The
first use of the term is for the set of functions such that...
The second is for a specific operation. Comes to the third use:

3. The *operation* of primitive recursion is exactly what programmers
call recursion.

In other words one specific and characteristic operation is used to
give the name to the set being defined.

> What you're failing to explain is why you would consider that function
> to be recursive from a programming standpoint.  

As for putting + under the format of primitive recursion, it would go
something like this (I guess)

Matching up that definition
Put
h is what is being defined ie + (or plus)
k = 1
f = id
g(y, ic, x) = S(ic) #ignore y and x, ic is internal (recursive) call

Gives

plus(0, x) = x
plus((S y), x) = S(plus(y, x))

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#5705

On Wed, May 18, 2011 at 9:15 AM, rusi <rustompmody@gmail.com> wrote:
>> What you're failing to explain is why you would consider that function
>> to be recursive from a programming standpoint.
>
> As for putting + under the format of primitive recursion, it would go
> something like this (I guess)
>
> Matching up that definition
> Put
> h is what is being defined ie + (or plus)
> k = 1
> f = id
> g(y, ic, x) = S(ic) #ignore y and x, ic is internal (recursive) call
>
> Gives
>
> plus(0, x) = x
> plus((S y), x) = S(plus(y, x))

You're still arguing mathematics.  I am not disputing that the
addition function is primitive recursive (in fact, I asserted that in
my original reply).  What I am saying is that this *implementation* of
the addition function:

def add(x, y):
  return y if x == 0 else add(x-1, y) + 1

is recursive in the programming sense (i.e. it uses the programming
technique of recursion), while this implementation is not:

def add(x, y):
  return x + y

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#5672

On Tue, 17 May 2011 15:26:42 -0700 (PDT), Xah Lee
  <xahlee@gmail.com> wrote:
:  If you look at Windows or Mac OS X world, i don't think they ever
:  refer to dealing with whole dir as “recursive” in user interface.

That's purely due to a difference in the level of abstraction.

Mac OS introduced its own vocabulary, of folders, where Unix and DOS
talked about directories.

A folder is a visual element on the screen; exactly modelling a paper
folder.  It goes without saying that if you bin a folder, the contents
goes with it.  Anything else would break the model and abstraction.

On Unix, the directory is just a file, listing other files by name
and disk location.  Then it is perfectly natural (although very
rarely smart) to delete a directory without any concequences to the
contents.  The data structure is clearly recursive; a file is either
an ordinary file or a directory, and a directory is a list of files.
An operation traversing the recursive data structure is recursive
regardless of how the algorithm is specified or implemented.

A large, although diminishing, fraction of Unix (excluding Mac OS)
users are likely to be familiar with the recursive structure of the
file system.

Now Mac OS X has maintained the folder concept of older mac generations,
and Windows has cloned it.  They do not want the user to understand
recursive data structures, and therefore, naturally, avoid the word.

-- 
:-- Hans Georg

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#5673

Hans Georg Schaathun <hg@schaathun.net> writes:

> On Unix, the directory is just a file, listing other files by name
> and disk location.  Then it is perfectly natural (although very
> rarely smart) to delete a directory without any concequences to the
> contents.  

Ironically, the only unix I know of where this makes a lot of sense is
Mac OS X (where multiple hard links to a single directory is utilised by
TimeMachine to minimise the size of incremental backup trees) :-)
-- 
  (espen)

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#5789

On 2011-05-18, Hans Georg Schaathun <hg@schaathun.net> wrote:
> Now Mac OS X has maintained the folder concept of older mac generations,
> and Windows has cloned it.  They do not want the user to understand
> recursive data structures, and therefore, naturally, avoid the word.

You imply they want to keep their users ignorant of these structures, as if
to keep something valuable from them. Wouldn't it be more honest, more to
the point and much simpler to state they don't NEED the user to understand
recursive - or indeed any other - data structures? And that the user doesn't
NEED to understand or know about them, just to use them?

After all they are users. They use their system for fun, learning or work.
Even a very competent or advanced use of a tool (computer, car, mobile phone,
fridge, TV, radio, toilet) in no way implies an understanding of it's inner
workings. Nor the need, nor the desire.



PS: Isn't this thread much ado about nothing?  :-)
It starts with the misconception (or should I say confusion?) between
performing a recursive job and using a recursive tool to do it. And then it
blazes off in these huge discusions about semantics to define a definition
of an abstraction of a alleady theoretical problem.

Glorious, just frelling glorious.    :-)
We have an expression for that. But I'll avoid using it, since it has the
word 'masturbation' in it...


And PPS: the P(P)S's don't specifically refer to your posting.


-- 
When in doubt, use brute force.
                -- Ken Thompson

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#5811

On Thu, 19 May 2011 23:21:30 +0200, Rikishi42
  <skunkworks@rikishi42.net> wrote:
:  On 2011-05-18, Hans Georg Schaathun <hg@schaathun.net> wrote:
: > Now Mac OS X has maintained the folder concept of older mac generations,
: > and Windows has cloned it.  They do not want the user to understand
: > recursive data structures, and therefore, naturally, avoid the word.
: 
:  You imply they want to keep their users ignorant of these structures, as if
:  to keep something valuable from them. Wouldn't it be more honest, more to
:  the point and much simpler to state they don't NEED the user to understand
:  recursive - or indeed any other - data structures? And that the user doesn't
:  NEED to understand or know about them, just to use them?

Admittedly, my wording had unintended implictions.  Mac OS X /targets/
users who do not need to understand the underlying structure.  However,
the system also has users who do.

:  After all they are users. They use their system for fun, learning or work.
:  Even a very competent or advanced use of a tool (computer, car, mobile phone,
:  fridge, TV, radio, toilet) in no way implies an understanding of it's inner
:  workings. Nor the need, nor the desire.

For a general purpose computer, that is simply not true in general.

:  PS: Isn't this thread much ado about nothing?  :-)

Most threads are.

:  It starts with the misconception (or should I say confusion?) between
:  performing a recursive job and using a recursive tool to do it. And then it
:  blazes off in these huge discusions about semantics to define a definition
:  of an abstraction of a alleady theoretical problem.

And explaining the source of the misconception and the varying use
would be irrelevant?

:  And PPS: the P(P)S's don't specifically refer to your posting.

Thanks :-) 

-- 
:-- Hans Georg

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#6088

On 2011-05-20, Hans Georg Schaathun <hg@schaathun.net> wrote:

>:  It starts with the misconception (or should I say confusion?) between
>:  performing a recursive job and using a recursive tool to do it. And then it
>:  blazes off in these huge discusions about semantics to define a definition
>:  of an abstraction of a alleady theoretical problem.
>
> And explaining the source of the misconception and the varying use
> would be irrelevant?

It usually is, yes. And boring.



-- 
When in doubt, use brute force.
                -- Ken Thompson

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#5813

On May 20, 2:21 am, Rikishi42 <skunkwo...@rikishi42.net> wrote:
> On 2011-05-18, Hans Georg Schaathun <h...@schaathun.net> wrote:
>
> > Now Mac OS X has maintained the folder concept of older mac generations,
> > and Windows has cloned it.  They do not want the user to understand
> > recursive data structures, and therefore, naturally, avoid the word.
>
> You imply they want to keep their users ignorant of these structures, as if
> to keep something valuable from them. Wouldn't it be more honest, more to
> the point and much simpler to state they don't NEED the user to understand
> recursive - or indeed any other - data structures? And that the user doesn't
> NEED to understand or know about them, just to use them?
>
> After all they are users. They use their system for fun, learning or work.
> Even a very competent or advanced use of a tool (computer, car, mobile phone,
> fridge, TV, radio, toilet) in no way implies an understanding of it's inner
> workings. Nor the need, nor the desire.
>
> PS: Isn't this thread much ado about nothing?  :-)
> It starts with the misconception (or should I say confusion?) between
> performing a recursive job and using a recursive tool to do it. And then it
> blazes off in these huge discusions about semantics to define a definition
> of an abstraction of a alleady theoretical problem.
>
> Glorious, just frelling glorious.    :-)
> We have an expression for that. But I'll avoid using it, since it has the
> word 'masturbation' in it...
>
> And PPS: the P(P)S's don't specifically refer to your posting.
>
> --
> When in doubt, use brute force.
>                 -- Ken Thompson

Well...
I was rethinking my earlier argument with Ian Kelly about the
similarity/differences between recursion in theory and in CS.
On rethinking my position I come to the conclusion that I am arguing
like an chimp -- and therefore not making my real point which is that
that recursion is more widespread in computer science than is
recognised.
This is discussed separately here

http://groups.google.com/group/comp.lang.python/browse_thread/thread/212e6477262125e9#

[I agree with you Xah that recursion is a technical word that should
not be foisted onto lay users.]

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#5827

On Thu, 19 May 2011 22:13:14 -0700, rusi wrote:

> [I agree with you Xah that recursion is a technical word that should not
> be foisted onto lay users.]

I think that is a patronizing remark that under-estimates the 
intelligence of lay people and over-estimates the difficulty of 
understanding recursion.

Any person who has ever been to a barber or hairdresser with mirrors on 
two parallel walls will be familiar with recursion: a reflection of the 
reflection of the reflection of the reflection, forever.

In 1970, an extremely low-brow comedy "Carry On Up The Jungle" was about 
the search for an imaginary bird that flies in smaller and small circles 
until it disappears up it's own rear end, a type of recursion: 

http://en.wikipedia.org/wiki/Carry_On_Up_the_Jungle

The bird in question goes back in folklore since at least 1854:

http://en.wikipedia.org/wiki/Oozlum_bird


Trust me on this, if the audience of Carry On films could understand 
recursion, anyone can!



-- 
Steven

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#5840

On 20 May 2011 06:55:35 GMT, Steven D'Aprano
  <steve+comp.lang.python@pearwood.info> wrote:
:  On Thu, 19 May 2011 22:13:14 -0700, rusi wrote:
: 
: > [I agree with you Xah that recursion is a technical word that should not
: > be foisted onto lay users.]
: 
:  I think that is a patronizing remark that under-estimates the 
:  intelligence of lay people and over-estimates the difficulty of 
:  understanding recursion.

Could we then say that «recursion is a technical word that should
not /unnecessarily/ be foisted onto lay users»?


-- 
:-- Hans Georg

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#5861

On May 20, 1:48 pm, Hans Georg Schaathun <h...@schaathun.net> wrote:
> On 20 May 2011 06:55:35 GMT, Steven D'Aprano  <steve+comp.lang.pyt...@pearwood.info> wrote:
>
> :  On Thu, 19 May 2011 22:13:14 -0700, rusi wrote:
> :
> : > [I agree with you Xah that recursion is a technical word that should not
> : > be foisted onto lay users.]
> :
> :  I think that is a patronizing remark that under-estimates the
> :  intelligence of lay people and over-estimates the difficulty of
> :  understanding recursion.
>
> Could we then say that «recursion is a technical word that should
> not /unnecessarily/ be foisted onto lay users»?

Yes.
Steven is talking about the fact that the intelligent lay user may be
intelligent.
I was referring to the fact that the intelligent lay user is a lay
user. [Not my main point except to say that dragging in
alt.usage.english into a discussion of recursion seemed a tad
unnecessary and unfair]

So the ILU may understand recursion
He may not know "recursion"

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