From: jweirich@...
Date: 2001-01-14T00:13:42+09:00
Subject: [ruby-talk:9246] Problems with obj.detect{} running in irb

Consider the following file "tree.rb" ...

----------------------------------------------------------------------
class Tree
  include Enumerable
  attr_reader :value
  attr_reader :left
  attr_reader :right
  def initialize(value, left=nil, right=nil)
    @value, @left, @right = value, left, right
  end
  def each(&block)
    yield @value
    @left.each &block  if @left
    @right.each &block if @right
  end
end
  
def createTree
  Tree.new(1,
	   Tree.new(2, Tree.new(3), Tree.new(4)),
	   Tree.new(5, Tree.new(6), Tree.new(7)))
end

def find(t,v)
  t.detect { |n| n==v }
end

$t = createTree
$t.each {|n| print n, " "}
p $t.detect { |n| n==3 }      # LINE A
----------------------------------------------------------------------

I can load and run the file from irb ...

    bash$ irb
    irb(main):001:0> load 'tree.rb'
    1 2 3 4 5 6 7 3
    3    
    true

But if I try to execute a line containing detect directly in irb
(e.g. LINE A above), I get ...

    irb(main):002:0> $t.detect { |n| n==3 }
    LocalJumpError: break from proc-closure
    (irb):2:in `each'
    ./tree.rb:11:in `each'
    (irb):2:in `detect'
    (irb):2:in `irb_binding'

Is this an irb problem, or a problem with my recursive definition of
each, or a combination?

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)