From: Christoph Rippel <crippel@...>
Date: 2001-03-07T03:10:02+09:00
Subject: [ruby-talk:12168] Re: disassembling and reassembling a hash


"Raja S." <raja@cs.indiana.edu> wrote in message
news:982srj$1p1$1@jetsam.uits.indiana.edu...
> ts <decoux@moulon.inra.fr> writes:
>
> >R>   keys,values = h.keys, h.values    # disassemble
> >R>   new_vals = norm_v (values)        # normalize
> >R>   Hash.make (keys, new_vals)        # reassemble
>
> >     h1 = {}
> >     h.each { |k, v| h1[k] = norm_v(v) }
>
> >   no ?
>
> Not quite.  v[i][j] is normalized based on -all- the values in v not just
> those in v[i].  Hence in the above norm_v (values) takes a vector of
vectors
> formed from the values of the hash.
>
> >>> p.s. is there a way to override a class method like Hash.new -without-
> >>> sub-classing?  It appears that class methods can't be aliased hence
> >>> redefinition of something like Hash.new doesn't seem possible?
>
>
> >   class Hash
> >      class << self
>     ...
>
> Aha!  'self' now refers to the class 'Hash' and by creating an anonymous
> super-class for it, class methods of 'Hash' become its instance methods
and
> hence can be aliased.  I didn't want to go "downwards" in terms of
creating
> a sub-class of Hash but didn't occur to me that one could go "upwards" and
> create an anonymous super-class!  Very nice and very clever!  Thank you.
Actually,

I am wondering about your interpretation - you are
actually going down-wards I believe -
If Hash would not be an object of type Class you
would be anonymously sub-typing (creating a singleton
class)  but since Hash is already a Class object non
(anonymous) sub-class is created - but I am not really
sure about this ...

[...]
> Question: since we have #to_a, #keys, #values --- all used to disassemble
a
>           hash would it be useful to enhance Hash.new(key,values) in the
>           core to assemble a hash from an array of keys and values?
>           Shouldn't break anything existing (I think).

I agree - you should post this as a RCR IMO (I would prefer a new class
function in Hash like Hash.make(keys,values))

Christoph

[...]