From: MonkeeSage <MonkeeSage@...>
Date: 2007-12-30T08:24:58+09:00
Subject: Re: Add Array#first= and Array#last= to std lib

On Dec 27, 1:58 pm, Sebastian Hungerecker <sep...@googlemail.com>
wrote:
> MonkeeSage wrote:
> > On Dec 27, 1:38 pm, Sebastian Hungerecker wrote:
> > > MonkeeSage wrote:
> > > > IOW, #pop returns a value, and this is just what #last does.
>
> > > How is [] different in that regard? That only returns a value, too.
>
> > Exactly. It's not... [] = 3 => syntax error...
>
> That [] there is an emtpy array. That's not the [] I was talking about.
> I'm sorry if I wasn't clear, let me rephrase:
> You seemed to say that while there is a method Array#[]= (which I assume,
> you're ok with, since you haven't stated otherwise), there shouldn't be a
> method Array#last= since Array#last only returns a value like Array#pop does.
> Now my question to you is: How is Array#[] different in that regard than
> Array#last? I mean some_array[-1] also only returns a value. But you don't
> have a problem with people being able to write some_array[-1] = some_value
> do you?
>
> --
> Jabber: sep...@jabber.org
> ICQ: 205544826

Sebastian (and Robert),

I guess I wasn't being very clear. By saying that #last just returns a
value like #pop, my point was that #last is the semantic equivalent of
the example I gave: "def l(a); a[-1]; end". I should have probably
compared it to #length rather than #pop since #pop is destructive.

I wasn't arguing for or against #last=, per se; I was only trying to
explain why it doesn't make sense, _to me_, "Unless the semantics [of
#last] change," to have #last=. I.e., #[] subscripts the array and
returns the value of the index, but #last returns the value of
subscripting the array at index #length-1; it is another level of
abstraction removed from #[]; so with those semantics, #last= would be
like #length= (or #pop=), and you end up with exceptions when the
value is immutable.

Regards,
Jordan