Re: unexpected +LOOP behavior

From	rickman <gnuarm@gmail.com>
Newsgroups	comp.lang.forth
Subject	Re: unexpected +LOOP behavior
Date	2015-05-26 15:09 -0400
Organization	A noiseless patient Spider
Message-ID	<mk2gad$iat$1@dont-email.me> (permalink)
References	(4 earlier) <55623fa0$0$2821$e4fe514c@news2.news.xs4all.nl> <mjtpra$6ji$1@dont-email.me> <mk2a0b$ohr$1@dont-email.me> <mk2d57$6qg$1@dont-email.me> <4_WdnWzkV5ryIPnInZ2dnUU7-VWdnZ2d@supernews.com>

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On 5/26/2015 2:37 PM, Elizabeth D. Rather wrote:
> On 5/26/15 8:15 AM, rickman wrote:
>> On 5/26/2015 1:20 PM, WJ wrote:
>>> Bernd Paysan wrote:
>>>
>>>>> But why are some Forth programmers so keen on their “all bits set”
>>>>> flag? Well, you can do neat things with it.
>>>>>
>>>>> : >CHAR DUP 9 > 7 AND + ASCII 0 + ;
>>>>>
>>>>> This will convert a digit to its ASCII representation. True, it
>>>>> is a clever piece of programming, but in our opinion it is bad
>>>>> style. Why? Because you are using a flag as a bitmask, which is a
>>>>> completely different datatype. Although there is no such thing as
>>>>> “data typing” in Forth, this way of programming makes it
>>>>> difficult to understand and maintain a program, which the
>>>>> ANS-Forth standard acknowledges:
>>>>
>>>> Honestly, this is only a problem if you don't know that idiom.
>>>
>>> That code is unreadable and unmaintainable.  It's very hard
>>> to figure out how it accomplishes its task.  I would not
>>> pay a programmer to produce code like that.
>>>
>>> This is somewhat more understandable:
>>>
>>> : >char
>>>    dup 9 > if [char] A 10 - else [char] 0 then
>>>    + ;
>>
>> If you have any reason to look at the definition of >char then I can't
>> see how you would not understand how it works.  Perhaps this would be a
>> better definition...
>>
>> \ Convert n to ASCII char
>> : >CHAR ( n -- char ) DUP 9 > 7 AND + ASCII 0 + ;
>>
>> Lol, saying it is unreadable and unmaintainable is a bit of a stretch. I
>> think that exact code has been read and understood as well as maintained
>> for many years now.  I am pretty sure I have seen something similar to
>> it way back when I was learning assembly language.  I think it took me
>> two minutes to see what it was doing.
>
> Indeed, proper documentation as in rickman's version above is essential
> to readable & maintainable code. Neither of the previous versions is
> acceptable, although I find the shorter code quite clear (and, as
> rickman notes, it's been around for many years). I would have preferred
> [CHAR] instead of ASCII, however, as it's Standard.

I had to "see" ASCII to find exactly what it did.  It seems to be state 
agnostic version of CHAR, [CHAR].  I wonder what that isn't used instead 
of the CHAR pair?  Sure seems simpler to use or am I opening a can of 
worms by asking?

-- 

Rick

Thread

unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-23 19:27 -0700
  Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-23 20:27 -0700
    Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-24 13:44 +0200
      Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-24 10:36 -0400
        Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-24 23:16 +0200
          Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 15:57 -0700
          Re: unexpected +LOOP behavior Bernd Paysan <bernd.paysan@gmx.de> - 2015-05-25 02:21 +0200
            Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-24 15:21 -1000
              Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 19:49 -0700
            Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 18:22 -0700
            Re: unexpected +LOOP behavior "WJ" <w_a_x_man@yahoo.com> - 2015-05-26 17:20 +0000
              Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-26 14:15 -0400
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-26 08:37 -1000
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-26 15:09 -0400
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-26 09:19 -1000
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-26 17:08 -0400
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-26 15:42 -0700
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-26 19:30 -0400
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-26 17:45 -0700
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-26 21:33 -0400
                Re: unexpected +LOOP behavior Coos Haak <chforth@hccnet.nl> - 2015-05-27 14:08 +0200
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-27 06:32 -0700
                Re: unexpected +LOOP behavior Coos Haak <chforth@hccnet.nl> - 2015-05-27 16:15 +0200
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-26 14:32 -1000
                Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-27 08:30 +0000
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-27 17:15 -0400
                Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-29 21:05 -0700
          Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-25 01:41 -0400
            Re: unexpected +LOOP behavior Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-05-24 23:26 -0700
              Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-25 14:33 +0000
              Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-25 10:56 -0400
                Re: unexpected +LOOP behavior Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-05-25 11:28 -0700
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-25 14:33 -0400
                Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-25 12:57 -0700
                Re: unexpected +LOOP behavior humptydumpty <ouatubi@gmail.com> - 2015-05-25 23:01 -0700
          Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-25 14:21 +0000
          Re: unexpected +LOOP behavior albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-05-26 23:59 +0000
          Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-27 09:15 +0000
            Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-27 10:06 +0000
            Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-27 12:03 -0400
              Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-27 16:23 +0000
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-27 12:39 -0400
            Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-27 22:14 +0200
              Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-27 17:13 -0400
                Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-27 23:36 +0200
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-27 18:06 -0400
                Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-29 10:35 +0200
                Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-29 12:16 +0100
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-29 09:42 -0400
                Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-29 16:16 +0200
                Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-29 15:24 +0100
              Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-27 17:32 -0400
                Re: unexpected +LOOP behavior Coos Haak <chforth@hccnet.nl> - 2015-05-27 23:59 +0200
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-27 19:31 -0400
                Re: unexpected +LOOP behavior Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-05-27 23:11 -0700
              Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-28 12:21 +0100
                Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-28 12:24 +0100
                Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-29 10:53 +0200
                Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-29 12:19 +0100
              Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-29 13:51 +0000
                Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-29 17:48 +0200
            Re: unexpected +LOOP behavior Bernd Paysan <bernd.paysan@gmx.de> - 2015-05-29 02:08 +0200
              Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-29 08:25 +0000
                Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-29 12:40 +0100
                Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-29 13:16 +0000
                Re: unexpected +LOOP behavior albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-05-29 18:43 +0000
                Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-29 20:08 +0100
                x86 tricks Lars Brinkhoff <lars.spam@nocrew.org> - 2015-06-05 09:42 +0200
                Re: x86 tricks albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-06-05 09:32 +0000
                Re: x86 tricks anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-05 09:40 +0000
                Re: x86 tricks albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-06-05 11:17 +0000
                Re: x86 tricks anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-05 15:49 +0000
                Re: x86 tricks "Alex McDonald" <blog@rivadpm.com> - 2015-06-05 17:45 +0100
                Re: x86 tricks anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-05 16:53 +0000
                Re: x86 tricks rickman <gnuarm@gmail.com> - 2015-06-07 13:20 -0400
                Re: x86 tricks anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-08 07:18 +0000
                Re: x86 tricks Bernd Paysan <bernd.paysan@gmx.de> - 2015-06-08 17:18 +0200
                Re: x86 tricks Tessa Bonting <tessa.bonting@gmail.com> - 2015-06-08 08:42 -0700
                Re: x86 tricks albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-06-06 09:47 +0000
                Re: x86 tricks anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-07 15:05 +0000
                Re: x86 tricks "Alex McDonald" <blog@rivadpm.com> - 2015-06-07 17:49 +0100
                Re: x86 tricks "Alex McDonald" <blog@rivadpm.com> - 2015-06-05 13:19 +0100
      Re: unexpected +LOOP behavior Mark Wills <markwills1970@gmail.com> - 2015-05-25 01:38 -0700
  Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-23 21:33 -0700
    Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-23 22:10 -0700
      Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-23 22:20 -0700
        Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-25 21:13 -0700
          Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-27 17:34 -0400
            Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-27 22:04 -0700
              Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-28 01:27 -0400
                Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-28 03:20 -0400
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-28 04:13 -0400
                Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-29 04:23 -0400
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-29 11:28 -0400
                Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-29 18:32 -0400
                Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-29 18:53 -0400
      Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-23 22:26 -0700
        Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-23 21:37 -1000
          Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 10:24 -0700
            Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-24 20:40 -0400
            Re: unexpected +LOOP behavior Hans Bezemer <the.beez.speaks@gmail.com> - 2015-05-25 14:08 +0200
              Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-25 17:27 -0400
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-25 14:47 -1000
                Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-27 17:33 -0400
            Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-25 12:53 -0700
              Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-25 13:05 -0700
              Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-25 14:49 -1000
                Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-25 18:03 -0700
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-05-25 16:44 -1000
                Re: unexpected +LOOP behavior humptydumpty <ouatubi@gmail.com> - 2015-05-25 22:56 -0700
                Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-26 08:05 +0000
        Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-24 10:43 -0400
          Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-24 08:29 -0700
            Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-24 15:44 +0000
              Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-27 00:57 -0700
              Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-06-05 13:11 -0700
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-06-05 12:24 -1000
                Re: unexpected +LOOP behavior JennyB <jennybrien@googlemail.com> - 2015-06-06 13:29 -0700
                Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-07 14:56 +0000
                Re: unexpected +LOOP behavior "Elizabeth D. Rather" <erather@forth.com> - 2015-06-07 10:38 -1000
                Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-06-08 08:08 +0000
        Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 10:01 -0700
      Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-24 10:40 -0400
        Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 11:29 -0700
          Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-25 09:51 -0700
            Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-25 10:44 -0700
              Re: unexpected +LOOP behavior "Alex McDonald" <blog@rivadpm.com> - 2015-05-25 12:34 -0700
                Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-25 12:59 -0700
  unexpected +LOOP behavior Mark Wills <markwills1970@gmail.com> - 2015-05-24 01:39 -0700
    Re: unexpected +LOOP behavior Coos Haak <chforth@hccnet.nl> - 2015-05-24 14:46 +0200
      Re: unexpected +LOOP behavior Mark Wills <markwills1970@gmail.com> - 2015-05-25 01:17 -0700
    Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-24 20:48 -0400
      Re: unexpected +LOOP behavior hughaguilar96@gmail.com - 2015-05-24 18:15 -0700
      Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-25 12:35 +0000
        Re: unexpected +LOOP behavior "Rod Pemberton" <fork@lllljunkqwer.cpm> - 2015-05-25 17:27 -0400
          Re: unexpected +LOOP behavior rickman <gnuarm@gmail.com> - 2015-05-25 18:16 -0400
            Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-25 16:17 -0700
              Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-25 17:16 -0700
                Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-25 17:50 -0700
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-25 18:47 -0700
              Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-25 20:01 -0700
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-25 20:29 -0700
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-25 20:32 -0700
              Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-26 08:03 +0000
                Re: unexpected +LOOP behavior Mark Wills <markwills1970@gmail.com> - 2015-05-26 01:10 -0700
                Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-26 22:31 -0700
                Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-26 20:07 -0700
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-26 20:20 -0700
                Re: unexpected +LOOP behavior Michael Barry <barrym95838@yahoo.com> - 2015-05-26 22:00 -0700
                Re: unexpected +LOOP behavior chitselb <chitselb@gmail.com> - 2015-05-27 02:41 -0700
  Re: unexpected +LOOP behavior anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-05-24 14:06 +0000

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