From: Eric Mahurin <eric_mahurin@...>
Date: 2005-08-03T07:34:27+09:00
Subject: Re: [RCR] array or with non-array

--- Simon Strandgaard <neoneye@gmail.com> wrote:

> Sometimes wish that  [3, 5, 13] | [8]  can be written as [3,
> 5, 13] | 8
> that  ary |= 42  would be possible.
> 
> chris2 pointed out that it would be inconsistent with [1,2,3]
> + 4.
> maybe let + append 4 to the array?
> 
> 
> 
> ary = [1, 3, 4]
> #=>  [1, 3, 4]
> 
> ary |= 2
> #=>  [1, 2, 3, 4]
> 
> 
> 
> This is another bad idea..


Are you suggesting this or saying it is bad?

I don't like it at all.  So this is suggesting 2 forms to
Array#| and Array#+:

array | other_array => array
array | element => array

If you are looking at combining an element that happens to also
be an array, you have an ambiguous situation.  It will combine
the contents of that array instead of the array.

If you want this functionality, you should ask for another
method that does this instead of overloading another.  There is
no disadvantage to this other than having to remember a new
method name (and not being able to reuse an operator).  The
problem is that there is a decision to be made about what to do
(combine a single element or an array of them) and that
decision is based on what the argument type is (or what methods
it responds to).  This goes clearly against the duck-typing
philosophy where a method should ignore the types of its
arguments - it should just use their methods and not worry.

OT ... but, the built-in classes of Ruby violate duck-typing
all over the place.  You'll find lots of examples where:

1) methods have multiple functionalities based on the types of
the arguments (usually exact class not just respond_to?).

2) even where a method only has one functionality (or the
multiple functionalites are determined by means other than arg
type/capabilities - flags, number of args, etc), many/most
built-in methods can't take args that have the same
capabilities as what is excepted - they only take a certain
type or maybe one derived from it.

I think this sucks about the Ruby library - that most builtin
methods have poor polymorphism/duck-typing of their arguments.



		
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