From: matz@... (Yukihiro Matsumoto)
Date: 2003-11-19T21:10:33+09:00
Subject: Re: Again, Rite explanation needed  (keyword args and new hash syntax)

Hi,

In message "Re: Again, Rite explanation needed  (keyword args and new hash syntax)"
    on 03/11/19, Greg McIntyre <greg@puyo.cjb.net> writes:

|I'm a bit confused by this too.
|
|---
|def f(a, b: 2, **kwd)
| p [a,b,kwd]
|end
|
|f(1) #=> [1,2,{}]
|f(1,b:5) #=>[1,5,{}]
|f(1,b:5,c:6) #=>[1,5,{:c=>6}]
|
|---
|
|Is the double asterisk (**) especially for grouping the rest of the
|arguments into a hash the same way that a single asterisk groups the
|rest of the arguments into an array? If so,

Basic Rule:
Double asterisk for grouping the rest of keyword arguments.  Keyword
arguments don't mix positional arguments (including optional ones).

|  f(1,b:5,6,7,8) # => ? runtime error?

Syntax Error.  Every keyword argument come after positional
arguments. 

|Can I still use position to in the argument list and forgo the
|keywordiness?
|
|  f(1,5) # => [1,5,{}]

Argument Error.  f() requires single positional argument, you
specified two.

|Can I change the order of the arguments or leave as many as I like out?
|Shouldn't that be included in the primary example of this? It is the
|point, isn't it?
|
|  def g(a:1,b:2,c:3)
|    [a,b,c]
|  end
|
|  g(c:5,b:6) # => [1, 6, 5]

Yes.  Order doesn't matter for keyword arguments.

							matz.