Re: Struggling with variable arguments to block

dblack wrote:
...
> I confess to confusion about the new arg/param semantics.  
> For example:

Me too - but I start seeing some light:-) Here is what
I got playing with this stuff (I guess you need a recent 
cvs version ...)

---
module Enumerable
   
  def each_one
    # turn an old style Hash#each
    # into a new style Hash#each
    each {|*e| yield *[e] }
  end
  
  def each_many
    # reverse of the above
    each {|e| yield *e }
  end 
  
  def sum
    result = 0
    each { |e| result += yield e }
    result
  end
  
  def sum_one
    result = 0
    each_one { |e| result += yield e }
    result
  end

  def sum_many
    result = 0
    each_many { |e| result += yield *e }
    result
  end

end

class << n = Object.new
  #  new style Hash::each
  include Enumerable
  def each
    yield [1,2]
    yield [3,4]
  end
end  

class << o = Object.new
  # old style Hash::each
  include Enumerable
  def each
    yield  1,2
    yield  3,4
  end
end

n.sum      {|a,b|  b } # fine
o.sum_one  {|a,b|  b } # fine
o.sum      {|a,b|  b } # warning
o.sum_many {|a,b|  b } # warning
# n.sum_one  {|a,b|  b } # Error ...
n.sum_many {|a,b|  b }  # warning
---

> 
>   irb(main):005:0> *a = 1,2
>   => [1, 2]
>   irb(main):006:0> *a = [1,2]
>   => [1, 2]
>   irb(main):007:0> *a = [[1,2]]
>   => [[[1, 2]]]
> 
> The one that doesn't seem to occur at all is [[1,2]] -- but 
> that's what the new Hash#each will give... but aren't block 
> semantics modeled on assignment semantics?  (I'm also still 
> puzzled about Proc.new {} and proc {} being different from 
> each other, but I'll settle for understanding |*a| for now :-)

I guess I'll settle for understanding the wisdom behind the recent    

enum.inject  {|a,b| break "me" if .. } 
enum.collect {|a|  break "me" if  .. }

change:-)

------------
/Christoph

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