From fbf05670850752e955aeb33fa87288df41421379 Mon Sep 17 00:00:00 2001
From: Keith Winstein <keithw@mit.edu>
Date: Thu, 13 Jan 2011 01:06:16 -0500
Subject: [PATCH] Screen out Ignore actions

---
 parser.cpp           | 29 ++++++++++++++++++-----------
 parserstate.hpp      |  4 ++--
 parsertransition.hpp |  4 ++--
 3 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/parser.cpp b/parser.cpp
index bb44442..932b3df 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -1,5 +1,20 @@
+#include <assert.h>
+#include <typeinfo>
+
 #include "parser.hpp"
 
+static void append_or_delete( Parser::Action *act,
+			      std::vector<Parser::Action *>&vec )
+{
+  assert( act );
+
+  if ( typeid( *act ) != typeid( Parser::Ignore ) ) {
+    vec.push_back( act );
+  } else {
+    delete act;
+  }
+}
+
 std::vector<Parser::Action *> Parser::Parser::input( wchar_t ch )
 {
   std::vector<Action *> ret;
@@ -7,21 +22,13 @@ std::vector<Parser::Action *> Parser::Parser::input( wchar_t ch )
   Transition tx = state->input( ch );
 
   if ( tx.next_state != NULL ) {
-    Action *exitact = state->exit();
-    if ( exitact ) {
-      ret.push_back( exitact );
-    }
+    append_or_delete( state->exit(), ret );
   }
 
-  if ( tx.action ) {
-    ret.push_back( tx.action );
-  }
+  append_or_delete( tx.action, ret );
 
   if ( tx.next_state != NULL ) {
-    Action *enteract = tx.next_state->enter();
-    if ( enteract ) {
-      ret.push_back( enteract );
-    }
+    append_or_delete( tx.next_state->enter(), ret );
     state = tx.next_state;
   }
 
diff --git a/parserstate.hpp b/parserstate.hpp
index 391cae7..2bfc236 100644
--- a/parserstate.hpp
+++ b/parserstate.hpp
@@ -18,8 +18,8 @@ namespace Parser {
   public:
     void setfamily( StateFamily *s_family ) { family = s_family; }
     Transition input( wchar_t ch );
-    virtual Action *enter( void ) { return NULL; }
-    virtual Action *exit( void ) { return NULL; }
+    virtual Action *enter( void ) { return new Ignore; }
+    virtual Action *exit( void ) { return new Ignore; }
 
     State() : family( NULL ) {};
     virtual ~State() {};
diff --git a/parsertransition.hpp b/parsertransition.hpp
index a1b03df..4d22998 100644
--- a/parsertransition.hpp
+++ b/parsertransition.hpp
@@ -26,12 +26,12 @@ namespace Parser {
     }
     virtual ~Transition() {}
 
-    Transition( Action *s_action=new Ignore(), State *s_next_state=NULL )
+    Transition( Action *s_action=new Ignore, State *s_next_state=NULL )
       : action( s_action ), next_state( s_next_state )
     {}
 
     Transition( State *s_next_state )
-      : action( new Ignore() ), next_state( s_next_state )
+      : action( new Ignore ), next_state( s_next_state )
     {}
   };
 }