[ruby-talk:13425] Re: Multidimensional arrays and hashes?

> From: [e-mail] [mailto:[e-mail]]On Behalf Of
[...]
> You only type less if you're doing it this way *once*.  If your
> program is filled with things like this ...
> 
>   h = {'a'=>{'b'=>{'c'=>'xxx'}}}
> 
> .. you end up typing a lot more than if you instantiate one `HashMD'
> object and then use lots of constructs like this:
> 
>   h['a']['b']['c'] = 'xxx'
> 
> However, in my opinion, saving a few keystrokes isn't very important
> at all.  To me, the advantage of the latter form is that it's much
> easier to read, understand, and maintain.

I guess that's a matter of taste (I was sort of wandering if 
h['a']['b']['c'] = 'xxx' should result 
{'c'=>{'b'=>{'a'=>'xxx'}}} or {{{'a'=>'b'} => 'c'}=>'xxx'} etc. ) 


> 
> Also, to me, a good idea would be to have some sort of mixin that can
> be included in Hash that can add a `get' and `set' method that look
> something like this:
> 
>   h.get('a','b','c')
> 
>   h.set('a','b','c','xxx')
> 
> The `get' method would return nil (or perhaps throw an exception) if a
> non-existent node is being referenced; and the `set' method would
> create the internal structure as needed.

but I agree that you probably want a short cut if you really use
this very often - I guess you want (you could use inject for this)
something like 

---------
module MultiHash
def lset! (*parms)
	raise TypeError.new 'lset - not enough parameters' if (nl = parms.length - 2)< 0
	tmp = self  
	for i in 0...nl do
		if (minitmp=  tmp[parms[i]]).kind_of? Hash 
				(tmp = minitmp)
			else
				minitmp= parms.last 
				nl.downto(i+1) { |j| minitmp={parms[j] => minitmp} }
				tmp[parms[i]] = minitmp
			return self
		end
		end
		if  (tmp.key? parms[nl]) && (parms.last == tmp[parms[nl]])
			return nil 	
	else
	tmp[parms[nl]] = parms.last	
		return self
	end
end
end


class Hash
include MultiHash
end

h ={}
p  h.lset!('a','b','c','x')
p  h.lset!('a','b','c','x')
p  h.lset!('a','b','C','x')
p  h.lset!('a','B','c','x')


Christoph