Support custom forkers

README.textile

@@ -68,6 +68,8 @@ Dataflow.local do |x, y, z|
   Thread.new { Dataflow.unify x, 1 }
   z #=> 6
 end
+
+# Note that a gobal Dataflow.declare is not supported
 </pre>
 
 <pre>
@@ -150,10 +152,6 @@ local do |x|
   end
   x #=> 1337
 end
-
-# NOTE: flow is used internally by need_later. This means that you
-# could override flow to do other things like use a threadpool,
-# and this would also affect need_later.
 </pre>
 
 <pre>
@@ -183,6 +181,29 @@ local do |queue, first, second|
 end
 </pre>
 
+h1. Debugging
+
+If you are having trouble and need to debug dataflow variables, simply call #inspect.
+
+If the variable has already been bound, it call inspect on its bound value like normal.However, if the variable is not bound yet then you will get a special string that contains the proxies #__id__ that you can use to track down which proxy objects are being passed around to which parts of your program:
+<pre>
+  local do |my_var| 
+    my_var.inspect # => #<Dataflow::Variable:2637860 unbound> 
+  end
+</pre>
+
+h1. Fork method customization
+
+By default both #flow and #need_later use Thread.fork as their fork method. Youc an access the fork method via Dataflow.forker.
+
+If you would like to use a custom forker, simple set it to a method that accepts and calls a block (for an example of a synchronous forker, see spec/forker_spec.rb):
+<pre>
+  Dataflow.forker = MyClass.method(:fork_with_threadpool)
+</pre>
+
+Also note that #flow is used interally by #need_later, in case you want to override that specifically.
+
+
 h1. Ports using Dataflow
 
 Ports are an extension of the declarative concurrent model to support nondeterministic behavior. They accomplish this through the use of a single state variable. Ports are also inspired by the Oz language.

dataflow.rb

@@ -2,6 +2,10 @@
 
 module Dataflow
   VERSION = "0.3.0"
+  class << self
+    attr_accessor :forker
+  end
+  self.forker = Thread.method(:fork)
 
   def self.included(cls)
     class << cls
@@ -36,7 +40,7 @@ def barrier(*variables)
   end
 
   def flow(output=nil, &block)
-    Thread.new do
+    Dataflow.forker.call do
       result = block.call
       unify output, result if output
     end

spec/forker_spec.rb

@@ -0,0 +1,28 @@
+require "#{File.dirname(__FILE__)}/spec_helper"
+
+describe 'Setting a customer forker' do
+  before(:all) do
+    @original_forker = Dataflow.forker
+    Dataflow.forker = Class.new do
+      def self.synchronous_forker(&block)
+        block.call
+      end
+    end.method(:synchronous_forker)
+  end
+
+  after(:all) do
+    Dataflow.forker = @original_forker
+  end
+
+  it 'uses the custom forker in #flow' do
+    local do |my_var|
+      flow(my_var) { 1337 }
+      my_var.should == 1337
+    end
+  end
+
+  it 'uses the custom forker in #need_later' do
+    my_var = need_later { 1337 }
+    my_var.should == 1337
+  end
+end