From: Yusuke Endoh <mame@...>
Date: 2011-12-26T23:28:36+09:00
Subject: [ruby-core:41814] Re: [ruby-trunk - Feature #5474][Assigned] keyword argument

Hello, Marc-Andre

2011/12/22, Marc-Andre Lafortune <ruby-core-mailing-list@marc-andre.ca>:
> While having fun testing your patch, I encountered an issue with more
> than 2 rest arguments:
>
>     def foo(*rest, b: 0, **options)
>       [rest, options]
>     end
>
>     foo(1, 2, bar: 0)  # => [[1, 2], {bar: 0}]  OK
>     foo(1, 2, 3, bar: 0)  # => [[1, 2, {bar: 0}], {bar: 0}]  Not OK

Good catch!  The commits I've done now include a fix for this.


> On 30 October 2011 11:10, Yusuke Endoh <mame@tsg.ne.jp> wrote:
>> Currently, my patch allows ** only when there are one or more
>> keyword arguments.
>>
>> This is because I didn't think of any use case.
>> In addition, I wanted to simplify the implementation of parser.
>> (Unfortunately, adding a new argument type requries *doubling*
>>  the parser rules to avoid yacc's conflict)
>> Do you think we need it?
>
> I'm worried about cases where one doesn't use named arguments directly
> but wants to pass them on to another method.

Indeed.  I've missed delegate.


>> I didn't implement caller's **.
>> I wonder if we need it or not.  Is "other(a, h)" not enough?
>
> I think one reason to have it is to avoid calling Hash#merge when
> combining options, like in the above examples.
>
> Instead of
>
>     def foo(bar: 42, **options)
>         baz(extra_option: 1, **options)
>     end
>
> Currently, one has to do:
>
>     def foo(bar: 42, **options)
>         baz(options.merge(extra_option: 1))
>     end

Oh yeah, I understand the use case.

I'll work for these two, after matz shows his opinion for
your new alternative syntax.  Thanks!

-- 
Yusuke Endoh <mame@tsg.ne.jp>