From: fREW <frioux@...>
Date: 2007-06-08T05:18:14+09:00
Subject: Re: What about a 'series' type?

On 6/7/07, Robert Dober <robert.dober@gmail.com> wrote:
> On 6/7/07, Robert Klemme <shortcutter@googlemail.com> wrote:
> > On 07.06.2007 16:52, Peter Marsh wrote:
> > >> primes = Series.new(Starting_value,Some_block_to_define_serires)
> > >
> > > Just wanted to be a bit clearer about this, the second argument is a
> > > block which can generate nth term in a series. This would probally take
> > > a while for primes, but if it were recursive then it would be easier...
> >
> > IMHO for a series it would be more natural to let the block calculate
> > a[n+1] from a[n] wouldn't it?  Of course, for Fibonacci this would only
> > work if you allow for multiple arguments.
> >
> > Something like
> >
> > #!ruby
> > class Serial
> >    include Enumerable
> >
> >    def initialize(*init, &f)
> >      @init = init
> >      @f = f
> >    end
> >
> >    def each(&b)
> >      a = b.arity
> >      current = @init
> >      loop do
> >        b[*current[0 ... a]]
> >        current = Array(@f[*current])
> >      end
> >      self
> >    end
> > end
> >
> > s1 = Serial.new 0 do |x| x+1 end
> > s1.each {|x| p x; break if x > 10}
> >
> > puts
> >
> > s2 = Serial.new 0,1 do |a,b| [b,a+b] end
> > s2.each {|x| p x; break if x > 40}
> >
>
> Robert I hope you do not mind my fantasy about/over/at??? your theme.
>
> class Serial
>   include Enumerable
>
>   def initialize(*init, &f)
>     @init = init
>     @f = f
>     @arity = f.arity
>   end
>
>   def get_some( some = nil, &b)
>     @current = @init.dup
>     if some && b.nil? then
>       (0...some).inject([]) do |acc,|
>         compute_next
>         acc << @current.first
>       end
>     else
>       a = b.arity
>       loop do
>         break if some && ( some -= 1 ) < 0
>         b[*@current.first( a )]
>         compute_next
>       end
>       self
>     end
>   end
>
>   private
>   def compute_next
>     @current += Array( @f[*@current] )
>     @current = @current.last @arity
>   end
> end
>
> s1 = Serial.new 0 do |x| x+1 end
> s1.get_some {|x| p x; break if x > 10}
> puts "-"*42
> puts s1.get_some(6)
>
> puts "-"*42
> f = Serial.new 1, 1 do |x, y| x + y end
> f.get_some(6){ |x,| puts x }
>
> puts "-"*42
> a = Serial.new 1, 1, 1 do |x, y, z| x + y + z end
> puts a.get_some(6)
>
> Cheers
> Robert
>
>
>
> --
> You see things; and you say Why?
> But I dream things that never were; and I say Why not?
> -- George Bernard Shaw
>
>

Isn't ruby cool?

-- 
-fREW