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Re: nested while loop computing triangular number - issues

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David Kleinecke <dkleinecke@gmail.com> writes:
> On Saturday, July 11, 2015 at 2:56:52 PM UTC-7, Keith Thompson wrote:
>> David Kleinecke <dkleinecke@gmail.com> writes:
>> [...]
>> > I have recently taken to writing this way - I repeat in my style:
>> >
>> >     int main (void) {
>> >         int n; 
>> >         int number;
>> >         int triangular_number;
>> >         int counter;
>> > #
>> >         n = 1;
>> >         counter = 1;
>> >         triangular_number = 0;
>> 
>> The use of "#" (a null preprocessor directive) is odd.  Perfectly legal,
>> but odd.  I might use an ordinary comment like:
>> 
>>     /******************/
>  
> I want something that looks to the eye like a blank line but isn't.
> A line like you show is too strong a divider. I want to write each
> function without any genuine blank lines (for other reasons) but I
> want to make a break equivalnt to a blank line. A single # resolves
> this conflict nicely.

Ok.  It's not what I'd do.  I might use "/**/", or "//" if I didn't
insist on C90.  I personally find your use of "#" a little jarring; null
directives are rarely used in practice, and I had to check the standard
to verify that a null directive does nothing.

Actually I'd just use a blank line.  You didn't say why you don't want
to do that; my best guess is that you want to use your editor's
paragraph movement commands.  You might investigate whether your editor
has commands to jump past C functions (vi/vim has "[[" and "]]").

But as I said, it's perfectly legal.

> ...
>
>> > Given compiler control I could extend C to allow an assignment (not an
>> > initialization 
>> >     local_variables = {1, 0, 1, 0,};
>> > Maybe this ia already a known extension.
>> 
>> It's not an extension; it's a standard language feature, starting with
>> C99, called "compound literals".
>> 
>>     local_variables = (struct foo){1, 0, 1, 0};
>> 
>> (Note that "(struct foo)" is not a cast; it's part of the syntax of the
>> compound literal.)
>> 
>> Of course if you insist on sticking to C90 you don't get to use things
>> like this.
>  
> I'll stay with C90. 
>
> That's an ugly syntax. Why is the non-cast necessary? What confict
> is resolved?

The type is necessary because without it the type of {1, 0, 1, 0}
would be indeterminate -- unless the type is inferred from the
context, but C expressions in general don't work that way.  Enclosing
the type in parentheses is, I presume, deliberately reminiscent of
cast syntax, and the stuff between the braces is explicitly defined
in the grammar as an initializer-list.  I don't disagree with your
statement that it's an ugly syntax, but it doesn't bother me much.

What alternative syntax would you suggest?

In any case, my main point stands; abandoning the advantage
of in-place initialization because you think of a collection of
local object declarations as a structure doesn't make much sense.
If you want to make it an actual structure, you can initialize
the structure.

(David, the following is unrelated to C90; you might want to stop
reading now.)

Incidentally, one thing I dislike about compound literals is that
the storage duration of the object depends only on the context in
which it appears.  A string literal always creates an array object
with static storage duration.  A compound literal creates an object
with static storage duration if it occurs outside a function,
or with automatic storage duration if it occurs inside a function.

It doesn't matter for the case we're discussing, but there are times
it would be convenient to have a block-scope compound literal that
refers to a static object.

I might suggest an enhancement that permits something like:

    (static struct foo){1, 0, 1, 0};

at block scope.  (Of course non-constant expressions would not
be permitted.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-11 06:31 -0700
  Re: nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-11 06:52 -0700
  Re: nested while loop computing triangular number - issues Siri Cruz <chine.bleu@yahoo.com> - 2015-07-11 07:07 -0700
    Re: nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-11 07:27 -0700
      Re: nested while loop computing triangular number - issues Siri Cruz <chine.bleu@yahoo.com> - 2015-07-11 08:19 -0700
  Re: nested while loop computing triangular number - issues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-11 15:28 +0100
    Re: nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-11 08:01 -0700
      Re: nested while loop computing triangular number - issues James Kuyper <jameskuyper@verizon.net> - 2015-07-11 12:24 -0400
      Re: nested while loop computing triangular number - issues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-11 21:24 +0100
        Re: nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-12 09:35 -0700
          Re: nested while loop computing triangular number - issues Keith Thompson <kst-u@mib.org> - 2015-07-12 11:55 -0700
            Re: nested while loop computing triangular number - issues Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-12 22:14 +0100
            Re: nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-13 08:05 -0700
    Re: nested while loop computing triangular number - issues David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 10:51 -0700
      Re: nested while loop computing triangular number - issues Keith Thompson <kst-u@mib.org> - 2015-07-11 14:56 -0700
        Re: nested while loop computing triangular number - issues David Kleinecke <dkleinecke@gmail.com> - 2015-07-12 09:32 -0700
          Re: nested while loop computing triangular number - issues James Kuyper <jameskuyper@verizon.net> - 2015-07-12 13:19 -0400
            Re: nested while loop computing triangular number - issues David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 10:16 -0700
          Re: nested while loop computing triangular number - issues Keith Thompson <kst-u@mib.org> - 2015-07-12 11:48 -0700
            Re: nested while loop computing triangular number - issues James Kuyper <jameskuyper@verizon.net> - 2015-07-12 15:23 -0400
            Re: nested while loop computing triangular number - issues Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-15 11:02 -0700
              Re: nested while loop computing triangular number - issues Keith Thompson <kst-u@mib.org> - 2015-07-15 13:19 -0700
                Re: nested while loop computing triangular number - issues Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 11:01 -0700
  Re: nested while loop computing triangular number - issues Alla _ <modelling.data@gmail.com> - 2015-07-11 08:45 -0700

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