From: Gavin Sinclair <gsinclair@...>
Date: 2002-09-24T16:22:25+09:00
Subject: Re: Picking arbitrary elements from an array


----- Original Message -----
From: <dblack@candle.superlink.net>


> >
> > How does this relate to Enumerable#select,
> > which Array mixes in? Do we somehow get
> > the functionality of both?
>
> Judging from some 1.7.3 experimenting, it seems that Array#select, if
> given an argument, acts like #indices, and if given a block but no
> argument, acts like #find_all (for which it used to be a synonym).  If
> given both, it raises an exception.
>
> I don't know if this is still under discussion, but in case it is...
> This new flavor of #select doesn't feel to me like it has the right
> name.  Maybe I'm just used to the idea of select as involving a test,
> rather than an index -- and in fact it still does, some of the time.
> It's really the same name for two very different things.
>
> My instincts, such as they are, would lead me to lean toward a
> multi-arg version of #at:
>
>   [1,2,3].at(1,2) => [2,3]
>
> Or is there (not for the first time) a subtlety or two I'm not
> getting?
>
>
> David
>

[1,3,6].at(1,2) => [3,6]        PROPOSED
[1,3,6].at(1)   => 3            ACTUAL
[1,3,6].at(1)   => [3]          CONSISTENT WITH PROPOSAL

#indices always returns an array, and has a really nice name, to boot.  I'm
sorry to see it go.

BTW it's very important to consistently return an array, in case you call it in
the following manner:

  indices = some_array
  values = arr.indices(*indices)

The subsequent code expects "values" to be an array, even if "indices" contains
zero or one elements.

I agree that overloading "select" for two different purposes is a bad idea.

Gavin