[ruby-core:36957] Re: [Ruby 1.9 - Feature #4824] Provide method Kernel#executed?

On Fri, Jun 10, 2011 at 10:03 AM, Cezary <[e-mail]> wrote:

> On Fri, Jun 10, 2011 at 07:20:32AM +0900, Rocky Bernstein wrote:
> >
> > Issue #4824 has been updated by Rocky Bernstein.
> >
> >
> > Cezary Baginski wrote:
> > > This may seem like heresy, but isn't really:
> > >
> > >   __FILE__ == $0
> > >
> > > just a hack for letting a file be *both* a script and a "library"
> > > at the same time? With the only sane use (I can think of) being
> > > adding unit tests?
> >
> > I wrote my thoughts regarding this to ruby-core on June 5-6. See
> > http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/36772.
>
> Yes, I read your comments (I read the list). It was what got me
> thinking. I didn't like checking using file path strings either.
>
> > It has one answer to your question which, in sum, is "demo code".
> > Demonstration code is not the same as a unit test.
>
> Yes, but shouldn't that be in a README or example.rb instead?
>

I prefer demo code to be runable in the same way that tests are runable. And
for simple things, one file is better, feels more lightweight, and is less
clumsy than e. If I want to copy, post or email the file, I'd rather do it
as one simple file when practical.

Sometimes I run the demo code up to some point in a debugger and then drop
into an irb. So think of this structure sort of like script/console of Ruby
on Rails, but for arbitrary Ruby classes and programs and where a certain
amount of needed program context has been set up by running the a portion of
the demo code, e.g. creating needed basic objects and hooking them together
if that is needed.


> > But there is another use. One can write a program that has a
> > command-line interface, but folks can use this as a library instead.
> > For example see, https://github.com/rocky/ps-watcher
>
> Shouldn't there be an executable script installed in bin/ loading a
> lib/ps-watcher/cli.rb file ?


You could do that. But for smaller things like programs like this, again, I
prefer not to do so.  But this is a matter of taste.

I think we can tolerate different styles, no?



> It would be accessible from $PATH.
> And unit/integration tests can be simpler and more robust.
>

If you looked at the project, you'll see that there are tests. I don't see
how unit/integration tests would be made simpler by putting the trivial
command-line interface, or main() routine, in another file.


> I understand the use case(s), but I don't see why '__FILE__ == $0' is
> really that useful and good practice enough to be explicitly supported
> by the language.
>

Austin Ziegler also described one of his uses for this idiom  which has a
slightly different purpose. He also expressed desire for this idiom. Could
it just be sufficient to accept that others find it useful even if it is not
useful to you?

This is now feels like discussions in Perl when folks would ask if "until"
was really important enough when there was "if" and "not" And if the form
with "statement if expression" was really warranted since you had "if
expression ...".

If you feel strongly about such matters, I suppose you could write a new
programming language or perhaps carve out a subset of Ruby that does not
have such things that you don't feel are useful or are good practice.


> As for the name - anything containing 'main' assumes familiarity with
> C-type languages, which may or may not be the case for novices.
>
> --
> Cezary Baginski
>
>