From: Robert Klemme <bob.news@...>
Date: 2004-09-20T16:59:40+09:00
Subject: Re: Array#index block and rdetect


"Yukihiro Matsumoto" <matz@ruby-lang.org> schrieb im Newsbeitrag
news:1095650370.096071.21408.nullmailer@x31.priv.netlab.jp...
> Hi,
>
> In message "Re: Array#index block and rdetect"
>     on Mon, 20 Sep 2004 11:12:12 +0900, "David A. Black"
<dblack@wobblini.net> writes:
>
> |>   * Enumerable#each_index should be removed (yes/no)
> |
> |There is no Enumerable#each_index -- nothing to remove.
>
> I meant each_with_index.
>
> |>   * How about other enumerable classes?
> |
> |I think the idea of every enumerable class having an "index", defined
> |as part of that class, is possibly useful.

Sorry, David, I stongly disagree: IMHO an index does only make sense in a
class that maintains a certain order (such as Array).  A Hash does not
have a particular order and thus Enumerable#each_with_index is the
appropriate thing; here the index is valid just for the current iteration
and can be used for printing or whatever.  But I would not want to add an
index to a Hash.

Or did you mean to use the hash key as index?  That would be a different
story...  While that would make sense for Array and Hash I think there are
a lot Enumerables out there that do not correspond easily to associative
storage, for example a Enumerable that emits arbitrary many random numbers
in its #each method.

>  For hashes it could be the
> |keys; for arrays, the integer index; for files, the line number.  In
> |some cases (like index/key for hashes), it might be redundant.  But it
> |might open up some good possibilities.
>
> The most consistent (but incompatible) change would be:
>
>   * leave Enumerable#each_with_index unchanged.
>   * make Hash#each as alias of Hash#each_value
>   * redefine Hash#each_with_index as alias of Hash#each_pair
>
> But this change may break many programs.

Yeah, that's true.  What about a method in Hash that changes method
behavior to the array compatible style?  That way no old code is broken
and you can purposely change a Hash's look if you need to make sure that
this Hash can be interchangeably used with an Array.

Kind regards

    robert