From: Simon Strandgaard <neoneye@...>
Date: 2004-05-07T18:19:30+09:00
Subject: Re: [ann] iterator-0.7

"Robert Klemme" <bob.news@gmx.net> wrote:
> "Simon Strandgaard" <neoneye@adslhome.dk> schrieb im Newsbeitrag
> news:20040506182920.02fd89f5.neoneye@adslhome.dk...
> > "Robert Klemme" <bob.news@gmx.net> wrote:
> > > Make Iterator::Concat#initialize to be able to do
> > > iterator = Iterator::Concat.new(i1, i2, i3) # brackets removed
> > > iterator = Iterator::Concat.new(i1, ary2, i3)
> > >
> >
> > Major dillema, I don't know how to do it.
> > My current Concat#initialize looks like  "def initialize(iterators,
> position=nil)"
> 
> Ah, I see.
> 
> > If I do "def initialize(*iterators, position=nil)".. that won't work ?
> >
> > irb(main):001:0> def m(*args, x=nil)
> > irb(main):002:1> p args
> > irb(main):003:1> p x
> > irb(main):004:1> end
> > SyntaxError: compile error
> > (irb):1: syntax error
> > def m(*args, x=nil)
> >               ^
> > (irb):1: syntax error
> >         from (irb):1
> > irb(main):005:0>
> >
> > Any hints on how to pass 'position' to initialize ?
> 
> def init(*args)
>   if Numeric === args[-1]
>     pos = args[-1]
>     args.slice!(-1, 1)
>   else
>     pos = nil
>   end
> 
>   puts "iterators: #{args.inspect}"
>   puts "position : #{pos.inspect}"
> end
> 

Hmmm.. maybe we are trying to put too much logic into
the initialize method. We could make a factory method for that.

class Concat
   def self.mk(*iterators); end
end




> irb(main):066:0> init "a","s",1
> iterators: ["a", "s"]
> position : 1
> => nil
> irb(main):067:0> init "a","s"
> iterators: ["a", "s"]
> position : nil
> => nil
> irb(main):068:0> init
> iterators: []
> position : nil
> => nil
> 
> Or even
> 
> def init2(*args)
>   pos = nil
>   iters = []
> 
>   args.each do |arg|
>     case arg
>       when Numeric
>         raise ArgumentError, "duplicate start positions" if pos
>         pos = arg
>       when Iterator # place appropriate type(s) here
>         iters << arg
>       when Enumerable
>         iters << Iterator::Continuation.new(arg, :each)
>       else
>         raise ArgumentError, "Don't know what to do with #{arg.inspect}"
>     end
>   end
> 
>   puts "iterators: #{iters.inspect}"
>   puts "position : #{pos.inspect}"
> end
> 

Bigger is better..  the factory method approach is visually better.


Interesting dillema though :-)

--
Simon Strandgaard