From: Simon Strandgaard <neoneye@...>
Date: 2005-07-19T21:58:53+09:00
Subject: Re: [RCR] nil for unassigned keys

On 7/19/05, Yukihiro Matsumoto <matz@ruby-lang.org> wrote:
>     on Tue, 19 Jul 2005 20:40:47 +0900, Simon Strandgaard <neoneye@gmail.com> writes:
> 
> |Sometimes I find myself writing  :key=>true,
> |it would be nice if one didn't had to do assignment,
> |so its value instead defaulted to nil.
> |
> |def test(hash={})
> |       p hash
> |end
> |
> |test('x', 'y'=>2, 'z')         #  {"x"=>nil, "y"=>2, "z"=>nil}
> 
> In that case, how can we distinguish a hash key without value and
> ordinal mandatory argument?

Maybe I don't understand the mandatory argument thing?
But can't you just count them somehow?

def test(arg1, arg2, hash={})
	puts "#{arg1.inspect} #{arg2.inspect} #{hash.inspect}"
end

# mandatory argument?
test(1, 2)           # 1 2 {}

# hash key without value
test(1, 2, 42)       # 1 2 {42=>nil}
test(1, 2, 3, 4)     # 1 2 {3=>nil, 4=>nil}
test(1, 2, 3, 4=>5)  # 1 2 {3=>nil, 4=>5}

--
Simon Strandgaard