From: Clemens Hintze <c.hintze@...>
Date: 2000-04-01T01:24:25+02:00
Subject: [ruby-talk:02318] Re: Question about attribute writers

Dave Thomas writes:
> Clemens Hintze <c.hintze@gmx.net> writes:
> 
> > At least I would expect it! It is like answered in your FAQ! How does
> > Ruby determine what a variable is? It is really stright-forward, IMHO.
> > 
> >    Look if there was an assignment before
> >       yes => compile a variable access
> >       no  => compile a method call.
> 
> True - I asked the wrong question. Rather than asking "is this the
> expected behavior", I guess I meant "is this the behavior that someone 
> would expect?" It seems to violate the principle of least surprise.

Hmm difficult thingy here, I think. I would never assume that 

   age = 12;

could invoke a method, because I *know* that this syntax normally
means assignment to a local variable. It would be very strange to me
to use a method 'age=', if I can access @age directly. Invoking a
method would furthermore be more costly.

I admit this it-could-be-a-variable-or-a-method-call thingy is one of
the things, that disturbes me also sometimes in Ruby.

> 
> Perhaps a warning would a good idea in these circumstances:
> 
>   warning: local variable eclipses instance method

Erhm ... IMHO this warning is wrong! Because there is *no*syntax* that
allow 'age = 12' meaning a method call to 'age='. So if this is
invalid syntax concerning the Ruby grammar, how could we issue a
warning that this method call would be globbered? We *are*not* able to
call the method like this. And if we use

   self.age = 12

as intended, all ambiguities are removed!

I would propose the opposite, if we really want to issue an
warning. The warning should be issued for the case

   age / 12

where I want to divide the value of a variable 'age'. But because this 
variable does not exists, I will get a method call compiled. Here the
compiler could issue an warning like:

   warning: ambigues variable access or method call

I could by-pass this warning then by explicitely writing:

   age() / 12

But I admit, that this solution would probably issue too much warnings
because the 'age / 12' syntax is often used!

Perhaps it would be better to not change anything, and describe this
case very carefully in the books and docs. Every language has its
gotchas. We cannot eliminate all of them. This is one of Ruby.

> 
> Dave

\cle

-- 
Clemens Hintze  mailto: c.hintze@gmx.net