Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: Loops (was Re: do { quit; } else { })
Date: Tue, 15 Apr 2025 11:30:24 +0100
Organization: A noiseless patient Spider
Lines: 106
Message-ID: <vtlcg0$3f46a$2@dont-email.me>
References: <vspbjh$8dvd$1@dont-email.me> <vt5js2$g1t7$1@dont-email.me>
 <20250409142303.00004645@yahoo.com> <87ikndqabc.fsf@nosuchdomain.example.com>
 <20250410115501.000037a5@yahoo.com> <vt8ei8$2vn84$1@dont-email.me>
 <20250410080629.532@kylheku.com> <vt94q5$3jjod$1@dont-email.me>
 <vt9628$3hhr8$3@dont-email.me> <vtammh$174ev$1@dont-email.me>
 <vtavn9$1dp7m$3@dont-email.me> <vtb8nv$1plb2$2@dont-email.me>
 <vtba81$1qfbm$1@dont-email.me> <vtbc6o$1te2o$1@dont-email.me>
 <vtbhjv$24api$1@dont-email.me> <vtbn2k$293r1$1@dont-email.me>
 <vtc19j$2kqlj$1@dont-email.me> <87a58mqt2o.fsf@nosuchdomain.example.com>
 <vtc7mp$2q5hr$1@dont-email.me> <vtcqf6$3j95s$1@dont-email.me>
 <vtdh4q$b3kt$1@dont-email.me> <vtf7fe$1qtpg$1@dont-email.me>
 <vtgfuf$31ug1$1@dont-email.me> <20250413072027.219@kylheku.com>
 <vtgpce$39229$1@dont-email.me> <vti2ki$g23v$1@dont-email.me>
 <vtin99$vu24$1@dont-email.me> <vtiuf0$18au8$1@dont-email.me>
 <vtj97r$1i3v3$1@dont-email.me> <vtl166$36p6b$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Tue, 15 Apr 2025 12:30:24 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="cec4580467d8bef69918f71b92c931ef";
	logging-data="3641546"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+6M62cJmo7SNkuvS+H/cay"
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:sQVnTBRdu3VeB0FG16R+9PWF984=
Content-Language: en-GB
In-Reply-To: <vtl166$36p6b$1@dont-email.me>
Bytes: 5522

On 15/04/2025 08:17, Janis Papanagnou wrote:
> On 14.04.2025 17:22, bart wrote:
>> On 14/04/2025 13:18, Janis Papanagnou wrote:
>>> (While there's some "C" stuff in here it contains a lot of non-"C"
>>> samples for comparison. So [OT]-sensible folks may want to skip this
>>> post.)
>>
>>> [...]
>>
>> I'm not saying there's anything wrong with it. The point was that an A
>> to B loop existed in the 1950s; C came out in the 1970s!
>>
>>> [...]
>> [...]
>>
>>> which of course would be written with a 'while'
>>>
>>>     int i = a;
>>>     while (i <= b) f(i++)
>>
>> That would be a poor use of 'while'.
> 
> Not the least.
> 
>> And bizarre, to use 'while' for
>> iteration, but 'for' for loops that are best written as while!
> 
> I was merely trying to provide some options to address your dislike.
> 
>>
>>> The "C" syntax has actually a flexibility that is very valuable.
>>
>> The flexibility is the problem, because you have to specify the loop in
>> such excruciating detail. It is easy to make a mistake which results in
>> still legal code. And you now have to analyse each loop to see what kind
>> of loop it is:
> 
> Well, our opinions obviously differ. I just give you two examples
> (and there's many variants of these) of not uncommon 'for' usages...
> 
>      for (c=0; bitstr; c++)
>          bitstr &= bitstr-1;

I can't grok that.

>      for (r=1; r<=0x80; r<<=1)
>          ...


> and someone already posted another iteration type on linked lists
> 
>      for (node = list; node; node = node->next)

These two I get, and I can tell you that they're all WHILE loops. To 
make make them tidier, I'd have fewer complaints about them if they 
instead looked like this:

   while (node = list; node; node = node->next)

So, you can optionally add extra elements to a while (x).

It would be necessary to either define whether while(x; y) means while 
(; x; y) or while (x; y), or to always require either zero or two 
semicolons inside (...).

That could have kept 'for' for how it works in other languages (the ones 
that haven't just blindly copied C's version!).


> The point here is the observation that there are loops that deviate
> from simple counted loops (and that are commonly used) and that they
> all comprise the same principal structure; initialization, condition
> test, change of loop-variables. The "C" loop syntax reflects that in
> its typical low-level syntax form. (I already said that personally I
> don't like "C"'s syntax, but I do like its flexibility.)

Let me ask you this: what exactly is the point of the 'while' statement 
in C? Since it can always be trivially be written as:

    for (;cond;)

It seems to that most use cases (initialise, check exit condition, 
change something that affects the letter), would suit 'for' better.

But since 'for' then becomes overloaded, there ought to be a dedicated 
feature for simple iteration. So it seems the solution is as a I 
suggested above.

>> [...]
>>
>> Suppose you see 'i <= N' as the condition; is that '<=' intentional, or
>> is it a typo for '<'? It's impossible to tell.
> 
> (This is nonsense.)

You can't just say that without explanation. WHY it it nonsense? Take this:

   for (i=0 i<=N; ++i)

Most such loops iterate over 0..N-1 inclusive, so would need "<". So, in 
your opinion, is that <= a typo, or is the intention to iterate over 
0..N inclusive (so N+1 iterations)?


(May reply to rest separately.)