Hi there,

we frequently do

ha = Hash.new {|h,k| h[k] = []}

so we can later do

ha[any_key] << anything

Since the idiom is so common, what does everybody think of putting it 
into the standard library:

def Hash.with_arrays
   new {|h,k| h[k] = []}
end

While we're at it, we might as well add

def Hash.with_hashes
   new {|h,k| h[k] = Hash.new(&h.default_proc)}
end

Kind regards

	robert