From: Eric Mahurin <eric_mahurin@...>
Date: 2005-07-20T00:58:08+09:00
Subject: Re: [RCR] nil for unassigned keys

--- Daniel Brockman <daniel@brockman.se> wrote:
> Thank you for your comments.
> >> This would also reasonably mean that mixing optional and
> >> mandatory arguments would become allowed:
> >>
> >>    def bar(a, b=nil, c, d=nil, e) ... end
> >>
> >>    bar 1                # ArgumentError
> >>    bar 1, 2             # ArgumentError
> >>    bar 1, 2, 3          # a=1, b=nil, c=2, d=nil, e=3
> >>    bar 1, 2, 3, 4       # a=1, b=2,   c=3, d=nil, e=4
> >>    bar 1, 2, 3, 4, 5    # a=1, b=2,   c=3, d=4,   e=5
> >
> > I don't like this. It is hard to see which value is put
> > into which parameter. Picking some arguments from the left
> > and from the right and stuffing the rest in the splatted
> > parameter is easier to grasp, at least for me.
> 
> Then what about this?
> 
>    def baz(a, b=nil, c) ... end
> 
> Isn't that just as easy to grasp as this?
> 
>    def baz(a, *b, c) ... end
> 
> > I think the chances to get the RCR accepted are higher if
> > you drop this feature.
> 
> You may be right.  But I think restricting this to “only if
> there's a splat argument somewhere!” is pretty arbitrary.
> 
> If you wanted the semantics of this,
> 
>    def baz(a, b=nil, c) ... end
> 
> you'd have to write it like this,
> 
>    def baz(a, *dummy, b=nil, c)
>      dummy.empty? or raise ArgumentError
>      ... end
> 
> which seems pretty annoying-for-no-reason.


Daniel,

I thought you were going to submit an RCR for this (not too
related to the original RCR topic of this thread - nil for
unassigned keys - of a hash).  Here is what was said in the
thread "Re: iterators and block arguments" (which covers your
concern above):

--- Eric Mahurin <eric_mahurin@yahoo.com> wrote:
> --- Daniel Brockman <daniel@brockman.se> wrote:
> 
> > Maybe this syntax could be adopted?
> > 
> >    def foo a, b, *args, c, d; ... end
> 
> I want that too.  It would be nice for the []= method where
> the
> value is always the last argument.  Or any method where you
> want optional arguments first or in the middle.
> 
> In general, this:
> 
> def foo a, b, c=x, d=y, *other, e, f
>     ...
> end
> 
> should be equivalent to:
> 
> def foo a, b, *remaining
>     e,f = remaining.slice!(-2,2)
>     c = remaining.empty? ? x : remaining.shift
>     d = remaining.empty? ? y : remaining.shift
>     other = remaining
>     ...
> end
> 
> Want to submit an RCR for this?  I've already done my fair
> share.



		
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