From: "Radosław Bułat" <radek.bulat@...>
Date: 2008-12-06T23:53:50+09:00
Subject: [ruby-core:20400] More powerful method arguments

(I'm thinking very loudly, don't get it to seriously)
I was thinking about "mandatory arguments after optional" in 1.9
lately and I cannot think about real use case with it but... if we can
do this

def foo(*args, options = {})
end

then we could use optional argument "options" like named arguments
list (which could be empty).
foo(1, 2, 3)
foo(1, 2, 3, controller: "foo", action: "bar")

It's almost the same as:

def foo(*args, options)
end

But in this case "options" isn't optional, and we must pass explicitly
empty hash {}.
foo(1, 2, 3, {})

It's very common idiom in Ruby to do that:
def foo(*args)
  options = args.last.is_a?(Hash) ? args.pop : {}
  # ...
end

$ pwd
/usr/lib/ruby/gems/1.8/gems
$ gem list | wc -l
275
$ grep -ER ".(last|\[-1\]).(is_a|kind_of|instance_of)\?[( ]Hash" . | wc -l
258

The point is that we can even make even more powerful (and
complicated) method arguments with allowing to place *args in any
place ;-).
def foo(*rest, a, b = 1, c, &block)
end

I think it shouldn't make method invocations ambiguous.
-- 
Radoslaw Bulat