From: dblack@...
Date: 2003-03-22T05:44:29+09:00
Subject: Re: Proposal: new operator: '<-' (for assignments)

Hi --

On Fri, 21 Mar 2003, Phil Tomson wrote:

> Since we can't override '=' (and it's a good idea that we can't) it seems
> that it would be nice to have another overridable operator for assigning
> values in classes.  So, I'm proposing that we allow a new operator '<-'
> (less-than minus) which can be overridden to allow assignment, for
> example:
>
> class Foo
>   def initialize(value)
>     @val = value
>   end
>
>   def <-(newVal)
>     @val = newVal
>   end
> end
>
> foo = Foo.new("this value")
> ....later...
> foo <- "some new value"
>
>
> Now of course, I could have allowed access to @val by declaring an
> attr_accessor, but in many cases I don't want to expose that information
> or make users of the class have to remember the name of the variable
> 'val'.  It just seems much cleaner in many cases to have an assignment
> operator.  Up till now I've been overriding '<<' to do this, but now I've
> run into a case where I'd like to pass on operators to the underlying
> value (@val in the example above) using method_missing so the underlying
> value can be shifted (and since '<<' is overriden, that's kind of tough).
>
> Thoughts?

This thread may have played out (you have to be awfully quick on the
button in ruby-talk these days!), but let me chime in anyway....

I don't think that what you're describing sounds like assignment; that
is:

  foo <- "some new value"

isn't actually assigning anything to foo.  So it just becomes, in a
sense, a kind of status-bestowing (because operator-like) method name,
which in the absence of its actually doing assignment I think is
potentially misleading.

Also, using a regular method name doesn't necessarily mean it has to
be named after a particular variable, so concerns about exposing
variable names wouldn't have to arise.  I'm thinking of things like:

  def reset_to(x)
    @val = x
  end

and so on, which don't use the attr_* family of shortcuts but might be
more suitable in a given case.


David

-- 
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav