From: John Gabriele <jmg3000@...>
Date: 2006-10-13T09:50:52+09:00
Subject: Re: Ruby expressions vs. values (like Perl?)

On 10/12/06, Booker C. Bense
<bbense+comp.lang.ruby.Oct.12.06@telemark.slac.stanford.edu> wrote:
> In article <65e0bb520610121433u151b89d9y1d757621bc4d41d3@mail.gmail.com>,
> John Gabriele <jmg3000@gmail.com> wrote:
> [snip]
> >
> >So, back to Ruby, I believe that the rhs of the following statement is
> >an "Array expression":
> >
> >irb(main):001:0> foo = ['a','bee','sea']
> >=> ["a", "bee", "sea"]
> >
> >but, what kind of expression is the rhs of the following:
> >
> >irb(main):002:0> bar = 'dee', 'ee', 'eff'
> >=> ["dee", "ee", "eff"]
> >
> >?
>
> One of the nice things about Ruby is that you can always ask it
> what it thinks.
>
> irb(main):090: bar.class
> => Array
> irb(main):010:0> bar.methods
> => ["respond_to?", "index", "select", "<<", "to_a", "delete_if",
> "slice", "&", "type", "each_index", "length",
> [snip]

Right. I see that bar is an Array, but I what I meant was, what kind
of expression is that comma-separated thingy on the right hand side
(when I made the assignment to bar)? Evidently, the answer seems to be
that ruby is allowing a little bit of extra syntactic sugar to make it
so I don't have to type those square brackets.

> >
> >Incidentally, I also note that this one -- although performing
> >parallel assignment -- also happens to be generating an Array value:
> >
> >irb(main):003:0> zz = ( a, b, c = 'gee', 'aitch', 'aye' )
> >=> ["gee", "aitch", "aye"]
> >
> >irb(main):004:0> zz
> >=> ["gee", "aitch", "aye"]
> >
> >According to irb, the Array gets generated even if you leave off the
> >"zz =" and the parentheses. Seems like extra work for the interpreter
> >to go through (making that Array), just to do a parallel assignment,
> >no?
>
> It's not making an Array, it's making a reference to an existing
> object.

Huh? irb seems to be clearly showing an Array. I'm thinking it's like
in C++ where you have this little short-lived temporary object. It
seems like it's an extra step for the interpreter to bother making
that extra temporary -- I'd think it could've just done the assignment
to a, b, and c and be done with it.

---John