From: Simon Strandgaard <0bz63fz3m1qt3001@...>
Date: 2003-06-09T20:59:36+09:00
Subject: Re: [RCR] join block

On Mon, 09 Jun 2003 11:21:35 +0900, Joel VanderWerf wrote:
> 
> I don't have any compelling examples. It's just that if someone said 
> "Now join takes a block", this is what I would guess it would do:
[snip]
> But that's just POLS for me, and IANYM.

POLS depends on your preferences and intuition.. I guess peoples intuition
differs.  'collect-join' seems most intuitive to me :-)  





How about both ideas (cjoin+pjoin) at the same time ?

> expand -t2 c.rb
class Array
  alias :oldjoin :join
  def pair_join(&block)
    lhs = first
    res = rhs = ""
    self[1..-1].each do |rhs|
      res += lhs.to_s + block.call(lhs, rhs)
      lhs = rhs
    end
    res + rhs.to_s
  end
  def collect_join(sep=$,, &block)
    collect { |y| block.call(y) }.oldjoin(sep)
  end
  def join(sep=$,, &block)
    return oldjoin(sep) if not block_given?
    return pair_join(&block) if block.arity == 2
    collect_join(sep, &block)
  end
end

def test_join
  puts "A: {"+[1,2,3,"a","b",5,"c"].join { |x, y|
    (x.class == y.class) ? "," : "} {" }+"}"
  puts "B: "+[1,2,3].join(", ") { |v| "(#{v})" }
  puts "C: "+[1,2,3].join { |v| "K#{v}O" }
  puts "D: "+[1,2,3].join("+")
  puts "E: "+[1,2,3].join
end

test_join
> ruby c.rb
A: {1,2,3} {a,b} {5} {c}
B: (1), (2), (3)
C: K1OK2OK3O
D: 1+2+3
E: 123
>

 
--
Simon Strandgaard