Re: function Is_Open (File : File_Type) return Boolean; :Text_io

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Wed, 28 Oct 2015 16:36:09 -0400, Bob Duff wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> On Wed, 28 Oct 2015 12:06:33 +0100, Georg Bauhaus wrote:
>>> However, another use of predicates is to document assumptions.
>>
>> Documenting *shall* have *no* run-time effects.
> 
> Really?!
> 
> In C, we can write:
> 
>     int num_gizmos = 0; // num_gizmos is always between 0 and 1024.
> 
> In Ada, we can write:
> 
>     type Gizmo_Count is range 0 .. 2**10;
>     Num_Gizmos: Gizmo_Count := 0;
> 
> IMHO, documenting the 0..1024 requirement in executable code is much
> better than using a comment:

How is that documenting? It is a direct instruction to the compiler.
Documentation is addressed to the human reader.

The advantage of Ada over C is that where in Ada you can instruct, in C the
only way is to document.

> By the way, what exactly do you mean by "shall"?  A native speaker of
> English doesn't usually use that word, except in legal documents and the
> like.  You seem to use the word "shall" to express opinions about the
> way things ought to be, which seems like an odd usage to me.

OK

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de