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Re: primitive instruction for programming

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From Steve Thompson <stevet810@gmail.com>
Newsgroups comp.lang.c
Subject Re: primitive instruction for programming
Date Tue, 14 Apr 2015 19:51:55 +0000
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On Mon, Apr 13, 2015 at 06:33:38PM -0500, Robert Wessel wrote:
> On Mon, 13 Apr 2015 18:20:38 -0500, Robert Wessel
> <robertwessel2@yahoo.com> wrote:
> 
> Code in haste, repent in leisure....
> 
> You have to actually put the root node on the stack in there
> somewhere, with something like a:
> 
>   push (traverse, rootnode);
> 
> before the loop.

So, your code should then look like:

>  node = rootnode;
>  push (end, NULL);
>  push (traverse, rootnode);
>  
>  for(;;)
>  {
>    pop item
>    if (item.type == end) break;
>    if (item.type == traverse)
>      {
>      if (item.node != NULL)
>        {
>        push (traverse, item.node->right);
>        push (output, item.node);
>        push (traverse, item.node->left);
>        }
>      }
>    if (item.type == output)
>      output item.node;
>  }

I can sort of see how that works, although your push and pop macro/
functions are not so clear but that is only a detail. I ought to have
implied that I merely had difficulty generating the algorithm without
gotos, as I have succeeded with (simplified):


    p = tree->root;

l1:
    if(p->left) {
        push(p, LEFT);
        p = p->left;
        goto l1;
    }

l2:
    do_something_to(p);

    if(p->right) {
        push(p, RIGHT);
        p = p->right;
        goto l1;
    }

l3:
    if(p == tree->root)
        goto next:

    pop(p, dir);

    if(dir == LEFT)
        goto l2;
    else
        goto l3;

next:


... which is reasonably straightforward but is bound to provoke people
who unconditionally dislike goto.  GCC allows one to take the address
of a label and so one can do something like the following:

   void *addr;

   p = tree->root;

l1:
    if(p->left) {
        push(p, &l2);
        p = p->left;
        goto l1;
    }

l2:
    do_something_to(p);

    if(p->right) {
        push(p, &l3);
        p = p->right;
        goto l1;
    }

l3:
    if(p == tree->root)
        goto next:

    pop(p, addr);

    goto *addr;


But the above reduces portability so I just use an int and the
comparison as in the first example.  The hard pard was finessing GCC
to allow using the processor stack as opposed to a stack-like
structure.



Regards,

Steve Thompson

-- 
"If I had a nickel for every time some idiot called me about a
computer problem that turned out to be user error, I would be able to
retire and spend the rest of my days cultivating clues in my backyard
hillside garden."  -- MysteryDog in 24hoursupport.helpdesk.

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primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 00:56 -0700
  Re: primitive instruction for programming Richard Heathfield <rjh@cpax.org.uk> - 2015-04-13 09:24 +0100
    Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 01:59 -0700
      Re: primitive instruction for programming Richard Heathfield <rjh@cpax.org.uk> - 2015-04-13 10:32 +0100
        Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 02:53 -0700
          Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 11:04 +0100
          Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-13 14:10 +0200
            Re: primitive instruction for programming Emiliano Gomes Padilha <egpadilha@gmail.com> - 2015-04-20 14:27 -0700
              Re: primitive instruction for programming Emiliano Gomes Padilha <egpadilha@gmail.com> - 2015-04-20 15:12 -0700
                Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-21 00:17 +0100
                Re: primitive instruction for programming Emiliano Gomes Padilha <egpadilha@gmail.com> - 2015-04-22 11:07 -0700
              Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-21 09:04 +0200
                Re: primitive instruction for programming Robert Wessel <robertwessel2@yahoo.com> - 2015-04-21 03:02 -0500
                Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-21 01:34 -0700
                Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-21 11:34 +0200
                Re: primitive instruction for programming Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-04-21 11:48 +0100
                Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-21 13:10 +0200
                Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-21 10:53 +0100
    Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 20:09 +0100
      Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 12:48 -0700
      Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-14 09:40 +0200
        Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-14 11:24 +0100
          Re: primitive instruction for programming Robert Wessel <robertwessel2@yahoo.com> - 2015-04-14 05:39 -0500
          Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-14 13:29 +0200
  Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 10:59 +0100
    Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 03:28 -0700
      Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 03:33 -0700
        Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 03:59 -0700
          Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 04:23 -0700
      Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 11:36 +0100
        Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 04:26 -0700
          Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 12:41 +0100
            Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 06:26 -0700
              Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-13 15:33 +0200
                Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 06:44 -0700
                Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-13 16:30 +0200
                Re: primitive instruction for programming Ian Collins <ian-news@hotmail.com> - 2015-04-14 07:52 +1200
                Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-14 09:47 +0200
                Re: primitive instruction for programming raltbos@xs4all.nl (Richard Bos) - 2015-04-14 08:10 +0000
                Re: primitive instruction for programming David Brown <david.brown@hesbynett.no> - 2015-04-14 10:40 +0200
        Re: primitive instruction for programming Steve Thompson <stevet810@gmail.com> - 2015-04-13 17:52 +0000
          Re: primitive instruction for programming Robert Wessel <robertwessel2@yahoo.com> - 2015-04-13 18:20 -0500
            Re: primitive instruction for programming Robert Wessel <robertwessel2@yahoo.com> - 2015-04-13 18:33 -0500
              Re: primitive instruction for programming Steve Thompson <stevet810@gmail.com> - 2015-04-14 19:51 +0000
          Re: primitive instruction for programming Tim Rentsch <txr@alumni.caltech.edu> - 2015-04-16 09:04 -0700
            Re: primitive instruction for programming Steve Thompson <stevet810@gmail.com> - 2015-04-17 02:25 +0000
              Re: primitive instruction for programming Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-17 08:34 -0700
                Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-17 17:49 +0100
                Re: primitive instruction for programming Steve Thompson <stevet810@gmail.com> - 2015-04-17 19:06 +0000
                Re: primitive instruction for programming Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-17 20:45 -0700
                Re: primitive instruction for programming Steve Thompson <stevet810@gmail.com> - 2015-04-18 16:43 +0000
                Re: primitive instruction for programming Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-18 09:56 -0700
                Re: primitive instruction for programming Stephen Sprunk <stephen@sprunk.org> - 2015-04-17 17:52 -0500
                Re: primitive instruction for programming Morris Dovey <mrdovey@iedu.com> - 2015-04-17 18:02 -0500
                Re: primitive instruction for programming Stephen Sprunk <stephen@sprunk.org> - 2015-04-17 19:26 -0500
                Re: primitive instruction for programming Morris Dovey <mrdovey@iedu.com> - 2015-04-17 20:04 -0500
                Re: primitive instruction for programming Michael Angelo Ravera <maravera@prodigy.net> - 2015-04-19 14:59 -0700
                Re: primitive instruction for programming Richard Heathfield <rjh@cpax.org.uk> - 2015-04-20 00:19 +0100
                Re: primitive instruction for programming Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-04-20 02:06 +0100
                Re: primitive instruction for programming Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-04-20 02:26 +0100
                Re: primitive instruction for programming Richard Heathfield <rjh@cpax.org.uk> - 2015-04-20 02:18 +0100
              Re: primitive instruction for programming Tim Rentsch <txr@alumni.caltech.edu> - 2015-04-18 18:59 -0700
                Re: primitive instruction for programming Steve Thompson <stevet810@gmail.com> - 2015-04-19 16:28 +0000
                Re: primitive instruction for programming Richard Damon <Richard@Damon-Family.org> - 2015-04-19 17:16 -0400
                Re: primitive instruction for programming Tim Rentsch <txr@alumni.caltech.edu> - 2015-04-22 15:28 -0700
          Re: primitive instruction for programming John Bode <jfbode1029@gmail.com> - 2015-04-23 07:20 -0700
  Re: primitive instruction for programming fmassei@gmail.com - 2015-04-13 03:07 -0700
    Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 09:47 -0700
      Re: primitive instruction for programming fmassei@gmail.com - 2015-04-13 11:09 -0700
        Re: primitive instruction for programming Noob <root@127.0.0.1> - 2015-04-13 20:43 +0200
          Re: primitive instruction for programming fmassei@gmail.com - 2015-04-13 12:09 -0700
            Re: primitive instruction for programming Xcott Craver <xcottcraver@gmail.com> - 2015-04-14 07:11 -0700
              Re: primitive instruction for programming fmassei@gmail.com - 2015-04-14 07:28 -0700
                Re: primitive instruction for programming Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-04-14 15:57 +0100
                Re: primitive instruction for programming fmassei@gmail.com - 2015-04-14 08:13 -0700
      Re: primitive instruction for programming fir <profesor.fir@gmail.com> - 2015-04-13 14:02 -0700
        Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 14:28 -0700
          Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 22:51 +0100
            Re: primitive instruction for programming fmassei@gmail.com - 2015-04-13 14:58 -0700
              Re: primitive instruction for programming Bartc <bc@freeuk.com> - 2015-04-13 23:25 +0100
                Re: primitive instruction for programming fmassei@gmail.com - 2015-04-13 15:37 -0700
                Re: primitive instruction for programming James Kuyper <jameskuyper@verizon.net> - 2015-04-13 19:09 -0400
                Re: primitive instruction for programming fmassei@gmail.com - 2015-04-13 16:20 -0700
                Re: primitive instruction for programming Robert Wessel <robertwessel2@yahoo.com> - 2015-04-13 18:03 -0500
            Re: primitive instruction for programming asetofsymbols@gmail.com - 2015-04-13 20:58 -0700
          Re: primitive instruction for programming fir <profesor.fir@gmail.com> - 2015-04-13 15:02 -0700

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