Re: [OT] Denis Ritchie Education

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.c
Subject	Re: [OT] Denis Ritchie Education
Date	2016-08-02 22:40 +0100
Organization	A noiseless patient Spider
Message-ID	<87inviu9w6.fsf@bsb.me.uk> (permalink)
References	(6 earlier) <1b8twfqlko.fsf@pfeifferfamily.net> <87ziovtcl6.fsf@bsb.me.uk> <1b4m73qeh7.fsf@pfeifferfamily.net> <87oa5bt3tq.fsf@bsb.me.uk> <00975844-42de-4ded-bee1-4a8a78ba0baa@googlegroups.com>

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supercat@casperkitty.com writes:

> On Tuesday, August 2, 2016 at 1:37:28 PM UTC-5, Ben Bacarisse wrote:
>> Ah, thanks.  I did not know that.  I would rule out (from being a
>> candidate for the first automatic computer) anything that can't do a
>> conditional branch (which presumably includes what we'd call a while
>> loop these days).
>
> Many old computers and control systems didn't need branches to be capable
> of looping.  Simply splice the end of the tape back to the beginning,

Although, without a choice being made, that's not what a while loop
does.

> or
> include a device to move cards back to the top of the hopper after they're
> processed.

and that's not automatic.  And if you automate the move, you again need
a conditional or you don't get a while loop.

> Various other kinds of conditional logic could be emulated
> using various kinds of arithmetic (if x is known to be 0 or 1, x ? y:z
> could be replaced with x*y + (1-x)*z, especially if multiplication by small
> values is fast.

Yes, you can do a little that way but halting is still a problem.
Formally, some machine's arithmetic are probably Turing complete which
is why I did not come done either way on the completeness issue -- I
just don't know enough about the issue.  I'd rather just say that I'd
want a more direct notion of choice when considering candidates.

-- 
Ben.

Thread

Re: [OT] Denis Ritchie Education "J. Clarke" <j.clarke.873638@gmail.com> - 2016-07-31 05:30 -0400
  Re: [OT] Denis Ritchie Education Tim Rentsch <txr@alumni.caltech.edu> - 2016-07-31 12:40 -0700
    Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-07-31 16:58 -0400
      Re: [OT] Denis Ritchie Education Tim Rentsch <txr@alumni.caltech.edu> - 2016-07-31 15:13 -0700
        Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-07-31 21:21 -0400
          Re: [OT] Denis Ritchie Education Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-01 08:12 -0700
      Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-07-31 16:41 -0600
        Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-07-31 21:24 -0400
          Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-07-31 22:15 -0600
            Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-01 09:38 -0400
              Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-01 10:18 -0600
                Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-01 16:22 -0400
                Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-01 15:05 -0600
                Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-04 14:01 -0400
                Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-04 12:22 -0600
                Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-04 16:47 -0400
                Re: [OT] Denis Ritchie Education "Osmium" <r124c4u102@comcast.net> - 2016-08-04 14:22 -0500
                Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-04 16:52 -0400
                Re: [OT] Denis Ritchie Education "Osmium" <r124c4u102@comcast.net> - 2016-08-04 16:10 -0500
                Re: [OT] Denis Ritchie Education Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-04 20:30 -0400
    Re: [OT] Denis Ritchie Education luser droog <luser.droog@gmail.com> - 2016-07-31 18:20 -0700
    Re: [OT] Denis Ritchie Education Gareth Owen <gwowen@gmail.com> - 2016-08-01 19:52 +0100
      Re: [OT] Denis Ritchie Education supercat@casperkitty.com - 2016-08-01 15:25 -0700
        Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-01 16:38 -0600
          Re: [OT] Denis Ritchie Education supercat@casperkitty.com - 2016-08-01 15:56 -0700
            Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-01 17:41 -0600
            Re: [OT] Denis Ritchie Education Gareth Owen <gwowen@gmail.com> - 2016-08-02 06:22 +0100
      Re: [OT] Denis Ritchie Education Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-01 16:48 -0700
        Re: [OT] Denis Ritchie Education Gareth Owen <gwowen@gmail.com> - 2016-08-02 06:27 +0100
          Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-02 08:42 -0600
            Re: [OT] Denis Ritchie Education Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-02 16:28 +0100
              Re: [OT] Denis Ritchie Education Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-08-02 11:15 -0600
                Re: [OT] Denis Ritchie Education Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-02 19:37 +0100
                Re: [OT] Denis Ritchie Education supercat@casperkitty.com - 2016-08-02 12:08 -0700
                Re: [OT] Denis Ritchie Education Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-02 22:40 +0100
          Re: [OT] Denis Ritchie Education Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-03 06:57 -0700
          Re: [OT] Denis Ritchie Education "J. Clarke" <j.clarke.873638@gmail.com> - 2016-10-30 09:06 -0400
            Re: [OT] Denis Ritchie Education supercat@casperkitty.com - 2016-10-30 12:42 -0700
            Re: [OT] Denis Ritchie Education Gareth Owen <gwowen@gmail.com> - 2016-10-31 18:12 +0000

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