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Re: Scope of identifiers

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David Kleinecke <dkleinecke@gmail.com> writes:
> On Tuesday, June 13, 2017 at 12:16:26 PM UTC-7, Keith Thompson wrote:
>> David Kleinecke <dkleinecke@gmail.com> writes:
[...]
>> > If one looks at the case of block scope and the old C approach
>> > one observes that all the declarations come before the statements.
>> > If one thinks of "starting" a scope extends through all the
>> > declarations then a single concept of "scope" holds.
>> >
>> > This observation doesn't help the present day situation but it does
>> > help explain how the situation cam about.
>> 
>> Given:
>> 
>>     {
>>         int a = 10;
>>         int b = a;
>>         int c = d; /* illegal */
>>         int d = 20;
>>         /* statements ... */
>>     }
>> 
>> the initialization of c is invalid because the scope of d doesn't start
>> until the line on which it's defined.
>> 
>> The lifetimes of all 4 objects begin at the same time, when
>> execution reaches the opening "{", but their scopes begin at 4
>> different locations.  All 4 scopes are the "same scope" as the
>> standard defines that phrase.  (Scope is a compile-time concept;
>> lifetime is a run-time concept.)
>> 
>> [...]
>  
> OK if you want to get pedantic.

What's pedantic about it?  You suggested

    If one thinks of "starting" a scope extends through all the
    declarations then a single concept of "scope" holds.

i.e., that the scope begins at the top of the block.  That's simply
incorrect.

>                                 In the sense of the statements -
> all the declarations happen first. They generally are such that
> they can be freely shuffled around.

As I demonstrated, they clearly can't if some declarations depend on
other declarations.

>                                     C has taken advantage of the
> fact that they have to be declared in some order to introduce
> more flexibility. It can be argued that initialization is a bad
> idea and should be avoided and if there are no initializations 
> the declarations can be made in any order.

Fortunately, I've never heard anyone argue that "initialization is
a bad idea and should be avoided".

> In other words in a primitive pre-C there was no initialization
> and the declarations could be thought of as simultaneous and all
> the scopes as the same. This simplicity is lost when initialization
> was introduced.  

I don't believe we were talking about "primitive pre-C".

-- 
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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Thread

Scope of identifiers Steve Keller <keller@no.invalid> - 2017-06-12 18:08 +0200
  Re: Scope of identifiers "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 12:22 -0400
    Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 09:39 -0700
  Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 09:38 -0700
    Re: Scope of identifiers "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 14:41 -0400
      Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 12:39 -0700
        Re: Scope of identifiers "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-12 15:53 -0400
          Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-12 13:19 -0700
            Re: Scope of identifiers David Kleinecke <dkleinecke@gmail.com> - 2017-06-13 11:01 -0700
              Re: Scope of identifiers jameskuyper@verizon.net - 2017-06-13 11:25 -0700
              Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-13 12:16 -0700
                Re: Scope of identifiers David Kleinecke <dkleinecke@gmail.com> - 2017-06-13 21:02 -0700
                Re: Scope of identifiers Ian Collins <ian-news@hotmail.com> - 2017-06-14 21:53 +1200
                Re: Scope of identifiers supercat@casperkitty.com - 2017-06-14 08:10 -0700
                Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-14 09:19 -0700
                Re: Scope of identifiers supercat@casperkitty.com - 2017-06-14 10:14 -0700
                Re: Scope of identifiers Keith Thompson <kst-u@mib.org> - 2017-06-14 09:12 -0700
  Re: Scope of identifiers Robert Wessel <robertwessel2@yahoo.com> - 2017-06-12 13:02 -0500

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