From: Florian Kaufmann <sensorflo@...>
Date: 2009-04-15T00:30:06+09:00
Subject: Argument types

The documentation of the standard classes/methods never mention of
what type/class an argument must be. For example let's look at the
subscript of an Array. There is the form "array[index]". But of what
Type must the index object be?
The ruby book tells me that programming ruby, types doesn't matter so
much, what matters is to what messages an object responds. Thus I
tried the following, thinking that to_i is needed so an object can be
used as an subscript index.

#!/usr/bin/ruby
class C
  def to_i
    0
  end
end
c = C.new
a = [0,1,2]
p a[c]

It doesn't work however:

./test:12:in `[]': can't convert C into Integer (TypeError)
	from ./test:12

So to which messages must C respond so objects of it can be used as
array index?

Flo