From: Christophe Grandsire <christophe.grandsire@...>
Date: 2005-10-21T18:33:32+09:00
Subject: Re: A comparison by example of keyword argument styles

Selon Robert Klemme <bob.news@gmx.net>:

>
>  - Mixing both styles for a single method feels not right in Ruby because
> it seems more complicated than necessary (just look at the length of the
> part of your discussion that deals with this).  Stored procedures of RDBMS
> can usually be called with parameters given either positional style *or*
> keyword style (btw, without a difference in declaration) but not mixed.  I
> would only allow one of the two approaches.
>

I'm afraid that would be too restrictive for Ruby. There are already cases (see
Rails for instance, as I learned it in another thread) where methods have
positional arguments followed by hash arguments, which may be advantagedly
replaced with positional arguments followed by keyword arguments. I think it
wouldn't fit with Ruby's dynamic argument passing to make positional and
keyword styles exclude each other.

On the other hand, you are right about one thing: if one is to allow all
arguments to be called either positionally or by keyword (the Sydney approach),
then the positional and keyword styles *must* exclude each other completely.
This is the only way we can prevent confusion.

However, I still think keyword arguments should be explicitly defined as such.

>  - Personally I'd probably favour an approach which allows only one
> calling style at a time.  Variables that have no default values declared
> will just be nil.  Basically this would be the equivalent of this with
> nicer syntax:
>
> old:
> def foo(h)
>   h[:length] * h[:width]
> end
>
> foo(:length => 10, :width => 20)
>
> new:
> def foo(length, width)
>   length * width
> end
> foo 10, 20
> foo width:20, length:10
>

Although I feel it's a bit too restrictive for Ruby, I could settle for that if
implicit keyword arguments win the debate. But I still prefer explicit ones.

On a side note, has the {a : 10, b : 20} alternative syntax for hashes that I've
seen proposed a long time ago been adopted?
--
Christophe Grandsire.

http://rainbow.conlang.free.fr

It takes a straight mind to create a twisted conlang.