--- a/configure.ac	Thu Feb 28 02:25:44 2013 -0500
+++ b/configure.ac	Thu Feb 28 10:53:27 2013 -0500
@@ -190,6 +190,17 @@
   AC_DEFINE(BOUNDS_CHECKING, 1, [Define to 1 to use internal bounds checking.])
 fi
 
+### Enable experimental push parser.
+
+OCTAVE_USE_PUSH_PARSER=no
+AC_ARG_ENABLE([push-parser],
+  [AS_HELP_STRING([--enable-push-parser],
+    [enable experimental push parser])],
+  [if test "$enableval" = yes; then OCTAVE_USE_PUSH_PARSER=yes; fi], [])
+if test $OCTAVE_USE_PUSH_PARSER = yes; then
+  AC_DEFINE(OCTAVE_USE_PUSH_PARSER, 1, [Define to 1 to use experimental push parser.])
+fi
+
 ### Use Octave's built-in memory allocator rather than straightforward malloc.
 ### Disabled by default.
 
@@ -2974,6 +2985,7 @@
   Build Java interface:               $build_java
   Do internal array bounds checking:  $BOUNDS_CHECKING
   Use octave_allocator:               $USE_OCTAVE_ALLOCATOR
+  Use push parser:                    $OCTAVE_USE_PUSH_PARSER
   Build static libraries:             $STATIC_LIBS
   Build shared libraries:             $SHARED_LIBS
   Dynamic Linking:                    $ENABLE_DYNAMIC_LINKING $DL_API_MSG

--- a/libinterp/parse-tree/oct-parse.yy	Thu Feb 28 02:25:44 2013 -0500
+++ b/libinterp/parse-tree/oct-parse.yy	Thu Feb 28 10:53:27 2013 -0500
@@ -166,6 +166,7 @@
 // object) relevant global values before and after the nested call.
 
 %define api.pure
+%define api.push-pull both
 %parse-param { octave_parser *curr_parser }
 %lex-param { void *scanner }
 
@@ -1479,10 +1480,66 @@
   curr_parser->bison_error (s);
 }
 
+octave_parser::~octave_parser (void)
+{
+#if defined (USE_PUSH_PARSER)
+  yypstate_delete (parser_state);
+#endif
+
+delete curr_lexer;
+}
+void octave_parser::init (void)
+{
+#if defined (USE_PUSH_PARSER)
+  parser_state = yypstate_new ();
+#endif
+
+  CURR_LEXER = curr_lexer;
+}
+
 int
 octave_parser::run (void)
 {
-  return octave_parse (this);
+  int status = 0;
+
+#if defined (USE_PUSH_PARSER)
+
+  for (;;)
+    {
+      unwind_protect frame;
+
+      frame.protect_var (current_input_line);
+
+      bool eof = false;
+
+      get_user_input (eof);
+
+      do
+        {
+          octave_char = eof ? END_OF_INPUT : octave_lex ();
+
+          if (octave_char == 0)
+            {
+              // Attempt to get more input.
+              status = -1;
+              break;
+            }
+
+          status = octave_push_parse (pstate);
+        }
+      while (status == YYPUSH_MORE);
+
+      if (status >= 0)
+        break;
+    }
+
+#else
+
+  status = octave_parse (this);
+
+#endif
+
+  return status;
 }
 
 // Error mesages for mismatched end tokens.

--- a/libinterp/parse-tree/parse.h	Thu Feb 28 02:25:44 2013 -0500
+++ b/libinterp/parse-tree/parse.h	Thu Feb 28 10:53:27 2013 -0500
@@ -144,15 +144,14 @@
       parsing_subfunctions (false), max_fcn_depth (0),
       curr_fcn_depth (0), primary_fcn_scope (-1),
       curr_class_name (), function_scopes (), primary_fcn_ptr (0),
-      curr_lexer (new lexical_feedback ())
+      curr_lexer (new lexical_feedback ()), parser_state (0)
   {
-    CURR_LEXER = curr_lexer;
+    init ();
   }
 
-  ~octave_parser (void)
-  {
-    delete curr_lexer;
-  }
+  ~octave_parser (void);
+
+  void init (void);
 
   void reset (void)
   {
@@ -389,6 +388,10 @@
   // State of the lexer.
   lexical_feedback *curr_lexer;
 
+  // Internal state of the parser.  Only used if USE_PUSH_PARSER is
+  // defined.
+  void *parser_state;
+
   // For unwind protect.
   static void cleanup (octave_parser *parser) { delete parser; }