From 714e1c0cecfed8e8aadfc223785b01cb7355f933 Mon Sep 17 00:00:00 2001
From: Jason Turner <lefticus@gmail.com>
Date: Mon, 29 Jun 2009 23:00:29 +0000
Subject: [PATCH] Support cleaner usage of bind, by adding a built in _
 variable

---
 dispatchkit/bootstrap.hpp       |  2 ++
 dispatchkit/proxy_functions.hpp | 10 ++++++++--
 samples/bind.chai               | 13 ++-----------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/dispatchkit/bootstrap.hpp b/dispatchkit/bootstrap.hpp
index 2ab934c..da32fa1 100644
--- a/dispatchkit/bootstrap.hpp
+++ b/dispatchkit/bootstrap.hpp
@@ -497,6 +497,8 @@ namespace dispatchkit
       s.register_function(boost::function<void ()>(boost::bind(&dump_system, boost::ref(s))), "dump_system");
       s.register_function(boost::function<void (Boxed_Value)>(boost::bind(&dump_object, _1)), "dump_object");
 
+      s.add_object("_", Placeholder_Object());
+
       s.register_function(boost::shared_ptr<Proxy_Function>(new Dynamic_Proxy_Function(boost::bind(&bind_function, _1))), 
           "bind");
 
diff --git a/dispatchkit/proxy_functions.hpp b/dispatchkit/proxy_functions.hpp
index 83f809f..06b1303 100644
--- a/dispatchkit/proxy_functions.hpp
+++ b/dispatchkit/proxy_functions.hpp
@@ -206,6 +206,10 @@ namespace dispatchkit
       boost::shared_ptr<Proxy_Function> m_guard;
   };
 
+  struct Placeholder_Object
+  {
+  };
+
   class Bound_Function : public Proxy_Function
   {
     public:
@@ -244,7 +248,8 @@ namespace dispatchkit
 
         while (true)
         {
-          while (barg != m_args.end() && !barg->is_unknown())
+          while (barg != m_args.end() 
+                 && !(barg->get_type_info() == Get_Type_Info<Placeholder_Object>::get()))
           {
             args.push_back(*barg);
             ++barg;
@@ -256,7 +261,8 @@ namespace dispatchkit
             ++parg;
           }
 
-          if (barg != m_args.end() && barg->is_unknown())
+          if (barg != m_args.end() 
+              && barg->get_type_info() == Get_Type_Info<Placeholder_Object>::get())
           {
             ++barg;
           } 
diff --git a/samples/bind.chai b/samples/bind.chai
index 4054357..e7aea7e 100644
--- a/samples/bind.chai
+++ b/samples/bind.chai
@@ -1,19 +1,10 @@
 
-//This is a cheater function. The entire point of it is to return a variable
-// with an unspecified type.
-// The bind function will substitute any unknown object with those passed in
-def _()
-{
-  var i;
-  return i;
-}
-
 def add(x, y)
 {
   return x + y;
 }
 
-var b = bind(add, 2, _());
+var b = bind(add, 2, _);
 var c = bind(b, 3);
 
 print(b(4));
@@ -25,7 +16,7 @@ def concat(a,b,c,d)
   return to_string(a) + to_string(b) + to_string(c) + to_string(d);
 }
 
-var d = bind(concat, _(), " Hello ", _(), " World ");
+var d = bind(concat, _, " Hello ", _, " World ");
 print(d(1, 3));
 //This checks to make sure arity is handled correctly:
 //print(d(1, 3, 4));