diff --git a/.gitignore b/.gitignore
index e05a551621bdb4230eeabf1e31cf7b053a1ef90c..721dcf9377a334d6d4f75617ea31df6f7c2ee639 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,3 +21,5 @@ Session.vim
 cscope.out
 build/
 .sconsign.dblite
+*.os
+*.pyc
diff --git a/.travis.yml b/.travis.yml
index 227698924e2edd1544fe184ca4d18e74f2594c9e..0e406ca5e19c45dc17a3c5ad4b85a86c0d9ebfef 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,4 +8,9 @@ before_install:
 script: 
   - scons
 notifications:
-  irc: "irc.upstandinghackers.com#hammer"
+  irc: 
+    channels: 
+      - "irc.upstandinghackers.com#hammer"
+    use_notice: true
+    skip_join: true
+        
diff --git a/SConstruct b/SConstruct
index 623bc5d8ef2ca99fe5ad79c5307426104078c736..50c185be815a8777c72f9cd550d00a70e6d0744e 100644
--- a/SConstruct
+++ b/SConstruct
@@ -8,7 +8,7 @@ vars = Variables(None, ARGUMENTS)
 vars.Add(PathVariable('DESTDIR', "Root directory to install in (useful for packaging scripts)", None, PathVariable.PathIsDirCreate))
 vars.Add(PathVariable('prefix', "Where to install in the FHS", "/usr/local", PathVariable.PathAccept))
 
-env = Environment(ENV = {'PATH' : os.environ['PATH']}, variables = vars)
+env = Environment(ENV = {'PATH' : os.environ['PATH']}, variables = vars, tools=['default', 'scanreplace'], toolpath=['tools'])
 
 def calcInstallPath(*elements):
     path = os.path.abspath(os.path.join(*map(env.subst, elements)))
@@ -28,11 +28,16 @@ if 'DESTDIR' in env:
 
 env['libpath'] = calcInstallPath("$prefix", "lib")
 env['incpath'] = calcInstallPath("$prefix", "include", "hammer")
-# TODO: Add pkgconfig
+env['parsersincpath'] = calcInstallPath("$prefix", "include", "hammer", "parsers")
+env['backendsincpath'] = calcInstallPath("$prefix", "include", "hammer", "backends")
+env['pkgconfigpath'] = calcInstallPath("$prefix", "lib", "pkgconfig")
+env.ScanReplace('libhammer.pc.in')
 
 env.MergeFlags("-std=gnu99 -Wall -Wextra -Werror -Wno-unused-parameter -Wno-attributes")
 
-if not env['PLATFORM'] == 'darwin':
+if env['PLATFORM'] == 'darwin':
+    env.Append(SHLINKFLAGS = ['-install_name', '$TARGET'])
+else:
     env.MergeFlags("-lrt")
 
 AddOption("--variant",
@@ -49,7 +54,12 @@ AddOption("--coverage",
           action="store_true",
           help="Build with coverage instrumentation")
 
-env['BUILDDIR'] = 'build/$VARIANT'
+AddOption("--in-place",
+          dest="in_place",
+          default=False,
+          action="store_true",
+          help="Build in-place, rather than in the build/<variant> tree")
+
 
 dbg = env.Clone(VARIANT='debug')
 dbg.Append(CCFLAGS=['-g'])
@@ -68,19 +78,33 @@ if GetOption("coverage"):
                LDFLAGS=["-fprofile-arcs", "-ftest-coverage"],
                LIBS=['gcov'])
 
+env["CC"] = os.getenv("CC") or env["CC"]
+env["CXX"] = os.getenv("CXX") or env["CXX"]
+
 if os.getenv("CC") == "clang" or env['PLATFORM'] == 'darwin':
     env.Replace(CC="clang",
                 CXX="clang++")
 
+env["ENV"].update(x for x in os.environ.items() if x[0].startswith("CCC_"))
+
 #rootpath = env['ROOTPATH'] = os.path.abspath('.')
 #env.Append(CPPPATH=os.path.join('#', "hammer"))
 
 Export('env')
 
-env.SConscript(["src/SConscript"], variant_dir='build/$VARIANT/src')
-env.SConscript(["examples/SConscript"], variant_dir='build/$VARIANT/examples')
+if not GetOption("in_place"):
+    env['BUILD_BASE'] = 'build/$VARIANT'
+    env.SConscript(["src/SConscript"], variant_dir='$BUILD_BASE/src')
+    env.SConscript(["examples/SConscript"], variant_dir='$BUILD_BASE/examples')
+else:
+    env['BUILD_BASE'] = '.'
+    env.SConscript(["src/SConscript"])
+    env.SConscript(["examples/SConscript"])
 
-env.Command('test', 'build/$VARIANT/src/test_suite', 'env LD_LIBRARY_PATH=build/$VARIANT/src $SOURCE')
+env.Command('test', '$BUILD_BASE/src/test_suite', 'env LD_LIBRARY_PATH=$BUILD_BASE/src $SOURCE')
 
 env.Alias("install", "$libpath")
 env.Alias("install", "$incpath")
+env.Alias("install", "$parsersincpath")
+env.Alias("install", "$backendsincpath")
+env.Alias("install", "$pkgconfigpath")
diff --git a/examples/base64_sem1.c b/examples/base64_sem1.c
index 46e58da23dcf49a7189c7d89a92ba8fff2780eea..4da171f355c9f8b7312ae29e231d58592602b901 100644
--- a/examples/base64_sem1.c
+++ b/examples/base64_sem1.c
@@ -23,7 +23,7 @@
 // They must be named act_<rulename>.
 ///
 
-HParsedToken *act_bsfdig(const HParseResult *p)
+HParsedToken *act_bsfdig(const HParseResult *p, void* user_data)
 {
     HParsedToken *res = H_MAKE_UINT(0);
 
@@ -54,7 +54,7 @@ H_ACT_APPLY(act_index0, h_act_index, 0);
 #define act_document     act_index0
 
 // General-form action to turn a block of base64 digits into bytes.
-HParsedToken *act_base64_n(int n, const HParseResult *p)
+HParsedToken *act_base64_n(int n, const HParseResult *p, void* user_data)
 {
     HParsedToken *res = H_MAKE_SEQN(n);
 
@@ -83,7 +83,7 @@ H_ACT_APPLY(act_base64_3, act_base64_n, 3);
 H_ACT_APPLY(act_base64_2, act_base64_n, 2);
 H_ACT_APPLY(act_base64_1, act_base64_n, 1);
 
-HParsedToken *act_base64(const HParseResult *p)
+HParsedToken *act_base64(const HParseResult *p, void* user_data)
 {
     assert(p->ast->token_type == TT_SEQUENCE);
     assert(p->ast->seq->used == 2);
diff --git a/examples/base64_sem2.c b/examples/base64_sem2.c
index 84155da23b7f09ca84a6487dedf031c27955e4e9..b7a2263efc1810a0140785f3494dc29a4d204f03 100644
--- a/examples/base64_sem2.c
+++ b/examples/base64_sem2.c
@@ -49,7 +49,7 @@ uint8_t bsfdig_value(const HParsedToken *p)
 // helper: append a byte value to a sequence
 #define seq_append_byte(res, b) h_seq_snoc(res, H_MAKE_UINT(b))
 
-HParsedToken *act_base64(const HParseResult *p)
+HParsedToken *act_base64(const HParseResult *p, void* user_data)
 {
     assert(p->ast->token_type == TT_SEQUENCE);
     assert(p->ast->seq->used == 2);
diff --git a/examples/dns.c b/examples/dns.c
index 3f730b970cd6d59677b7d8a38dcec8ea7b10ef48..63df3a443377dfd93717f091d107ffbccb41ac05 100644
--- a/examples/dns.c
+++ b/examples/dns.c
@@ -15,7 +15,7 @@
 // Validations
 ///
 
-bool validate_hdzero(HParseResult *p) {
+bool validate_hdzero(HParseResult *p, void* user_data) {
   if (TT_UINT != p->ast->token_type)
     return false;
   return (0 == p->ast->uint);
@@ -25,7 +25,7 @@ bool validate_hdzero(HParseResult *p) {
  * Every DNS message should have QDCOUNT entries in the question
  * section, and ANCOUNT+NSCOUNT+ARCOUNT resource records.
  */
-bool validate_message(HParseResult *p) {
+bool validate_message(HParseResult *p, void* user_data) {
   if (TT_SEQUENCE != p->ast->token_type)
     return false;
 
@@ -86,7 +86,7 @@ void set_rdata(struct dns_rr *rr, HCountedArray *rdata) {
   }
 }
 
-HParsedToken* act_header(const HParseResult *p) {
+HParsedToken* act_header(const HParseResult *p, void* user_data) {
   HParsedToken **fields = h_seq_elements(p->ast);
   dns_header_t header_ = {
     .id     = H_CAST_UINT(fields[0]),
@@ -109,7 +109,7 @@ HParsedToken* act_header(const HParseResult *p) {
   return H_MAKE(dns_header_t, header);
 }
 
-HParsedToken* act_label(const HParseResult *p) {
+HParsedToken* act_label(const HParseResult *p, void* user_data) {
   dns_label_t *r = H_ALLOC(dns_label_t);
 
   r->len = h_seq_len(p->ast);
@@ -121,7 +121,7 @@ HParsedToken* act_label(const HParseResult *p) {
   return H_MAKE(dns_label_t, r);
 }
 
-HParsedToken* act_rr(const HParseResult *p) {
+HParsedToken* act_rr(const HParseResult *p, void* user_data) {
   dns_rr_t *rr = H_ALLOC(dns_rr_t);
 
   rr->name     = *H_FIELD(dns_domain_t, 0);
@@ -136,7 +136,7 @@ HParsedToken* act_rr(const HParseResult *p) {
   return H_MAKE(dns_rr_t, rr);
 }
 
-HParsedToken* act_question(const HParseResult *p) {
+HParsedToken* act_question(const HParseResult *p, void* user_data) {
   dns_question_t *q = H_ALLOC(dns_question_t);
   HParsedToken **fields = h_seq_elements(p->ast);
 
@@ -153,7 +153,7 @@ HParsedToken* act_question(const HParseResult *p) {
   return H_MAKE(dns_question_t, q);
 }
 
-HParsedToken* act_message(const HParseResult *p) {
+HParsedToken* act_message(const HParseResult *p, void* user_data) {
   h_pprint(stdout, p->ast, 0, 2);
   dns_message_t *msg = H_ALLOC(dns_message_t);
 
diff --git a/examples/dns_common.c b/examples/dns_common.c
index 01dd8f0fb4630680174f8fff657c70f845775624..bf934d6184190d419495aa6011118d5a67e4f7fa 100644
--- a/examples/dns_common.c
+++ b/examples/dns_common.c
@@ -10,7 +10,7 @@ H_ACT_APPLY(act_index0, h_act_index, 0)
 /**
  * A label can't be more than 63 characters.
  */
-bool validate_label(HParseResult *p) {
+bool validate_label(HParseResult *p, void* user_data) {
   if (TT_SEQUENCE != p->ast->token_type)
     return false;
   return (64 > p->ast->seq->used);
@@ -18,7 +18,7 @@ bool validate_label(HParseResult *p) {
 
 #define act_label h_act_flatten
 
-HParsedToken* act_domain(const HParseResult *p) {
+HParsedToken* act_domain(const HParseResult *p, void* user_data) {
   HParsedToken *ret = NULL;
   char *arr = NULL;
 
diff --git a/examples/dns_common.h b/examples/dns_common.h
index 8af014b2f22c28da36e3312b56e355e1d5500e73..3e30770ad60a6acd4f375f2d36b5a9def5c8906a 100644
--- a/examples/dns_common.h
+++ b/examples/dns_common.h
@@ -7,6 +7,6 @@
 HParser* init_domain();
 HParser* init_character_string();
 
-HParsedToken* act_index0(const HParseResult *p);
+HParsedToken* act_index0(const HParseResult *p, void* user_data);
 
 #endif
diff --git a/examples/rr.c b/examples/rr.c
index dd250637a7eaccf1074f9441bb6d273452cc130d..c179922d664986be6277748c55e9050d1bfcb687 100644
--- a/examples/rr.c
+++ b/examples/rr.c
@@ -11,13 +11,13 @@
 // Validations and Semantic Actions
 ///
 
-bool validate_null(HParseResult *p) {
+bool validate_null(HParseResult *p, void* user_data) {
   if (TT_SEQUENCE != p->ast->token_type)
     return false;
   return (65536 > p->ast->seq->used);
 }
 
-HParsedToken *act_null(const HParseResult *p) {
+HParsedToken *act_null(const HParseResult *p, void* user_data) {
   dns_rr_null_t *null = H_ALLOC(dns_rr_null_t);
 
   size_t len = h_seq_len(p->ast);
@@ -28,7 +28,7 @@ HParsedToken *act_null(const HParseResult *p) {
   return H_MAKE(dns_rr_null_t, null);
 }
 
-HParsedToken *act_txt(const HParseResult *p) {
+HParsedToken *act_txt(const HParseResult *p, void* user_data) {
   dns_rr_txt_t *txt = H_ALLOC(dns_rr_txt_t);
 
   const HCountedArray *arr = H_CAST_SEQ(p->ast);
@@ -47,7 +47,7 @@ HParsedToken *act_txt(const HParseResult *p) {
   return H_MAKE(dns_rr_txt_t, txt);
 }
 
-HParsedToken* act_cstr(const HParseResult *p) {
+HParsedToken* act_cstr(const HParseResult *p, void* user_data) {
   dns_cstr_t *cs = H_ALLOC(dns_cstr_t);
 
   const HCountedArray *arr = H_CAST_SEQ(p->ast);
@@ -60,7 +60,7 @@ HParsedToken* act_cstr(const HParseResult *p) {
   return H_MAKE(dns_cstr_t, cs);
 }
 
-HParsedToken* act_soa(const HParseResult *p) {
+HParsedToken* act_soa(const HParseResult *p, void* user_data) {
   dns_rr_soa_t *soa = H_ALLOC(dns_rr_soa_t);
 
   soa->mname   = *H_FIELD(dns_domain_t, 0);
@@ -74,7 +74,7 @@ HParsedToken* act_soa(const HParseResult *p) {
   return H_MAKE(dns_rr_soa_t, soa);
 }
 
-HParsedToken* act_wks(const HParseResult *p) {
+HParsedToken* act_wks(const HParseResult *p, void* user_data) {
   dns_rr_wks_t *wks = H_ALLOC(dns_rr_wks_t);
 
   wks->address  = H_FIELD_UINT(0);
@@ -87,7 +87,7 @@ HParsedToken* act_wks(const HParseResult *p) {
   return H_MAKE(dns_rr_wks_t, wks);
 }
 
-HParsedToken* act_hinfo(const HParseResult *p) {
+HParsedToken* act_hinfo(const HParseResult *p, void* user_data) {
   dns_rr_hinfo_t *hinfo = H_ALLOC(dns_rr_hinfo_t);
 
   hinfo->cpu = *H_FIELD(dns_cstr_t, 0);
@@ -96,7 +96,7 @@ HParsedToken* act_hinfo(const HParseResult *p) {
   return H_MAKE(dns_rr_hinfo_t, hinfo);
 }
 
-HParsedToken* act_minfo(const HParseResult *p) {
+HParsedToken* act_minfo(const HParseResult *p, void* user_data) {
   dns_rr_minfo_t *minfo = H_ALLOC(dns_rr_minfo_t);
 
   minfo->rmailbx = *H_FIELD(dns_domain_t, 0);
@@ -105,7 +105,7 @@ HParsedToken* act_minfo(const HParseResult *p) {
   return H_MAKE(dns_rr_minfo_t, minfo);
 }
 
-HParsedToken* act_mx(const HParseResult *p) {
+HParsedToken* act_mx(const HParseResult *p, void* user_data) {
   dns_rr_mx_t *mx = H_ALLOC(dns_rr_mx_t);
 
   mx->preference = H_FIELD_UINT(0);
@@ -184,7 +184,7 @@ HParser* init_rdata(uint16_t type) {
   for(uint16_t i = 0; i<RDATA_TYPE_MAX+1; i++) {
     if(parsers[i]) {
       parsers[i] = h_action(h_sequence(parsers[i], h_end_p(), NULL),
-			    act_index0);
+			    act_index0, NULL);
     }
   }
 
diff --git a/libhammer.pc.in b/libhammer.pc.in
new file mode 100644
index 0000000000000000000000000000000000000000..97ded13f8806ab4e3146f9cb79924dfa52521cc7
--- /dev/null
+++ b/libhammer.pc.in
@@ -0,0 +1,10 @@
+prefix=/usr
+exec_prefix=${prefix}
+includedir=${prefix}/include
+libdir=${exec_prefix}/lib
+
+Name: libhammer
+Description: The Hammer parsing library
+Version: 0.9.0
+Cflags: -I${includedir}/hammer
+Libs: -L${libdir} -lhammer
diff --git a/src/SConscript b/src/SConscript
index cb5d7f6cfaa1e383aa7f08bee13437aa8bb7e67c..0cb41af72a02f3f43cba8f1c1093aed4eda407de 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -6,7 +6,17 @@ bindings = ['python']
 dist_headers = [
     "hammer.h",
     "allocator.h",
-    "glue.h"
+    "glue.h",
+    "internal.h"
+]
+
+parsers_headers = [
+    "parsers/parser_internal.h"
+]
+
+backends_headers = [
+    "backends/regex.h",
+    "backends/contextfree.h"
 ]
 
 parsers = ['parsers/%s.c'%s for s in
@@ -49,6 +59,7 @@ misc_hammer_parts = [
     'glue.c',
     'hammer.c',
     'pprint.c',
+    'registry.c',
     'system_allocator.c']
 
 tests = ['t_benchmark.c',
@@ -63,6 +74,9 @@ libhammer_static = env.StaticLibrary('hammer', parsers + backends + misc_hammer_
 
 env.Install("$libpath", [libhammer_static, libhammer_shared])
 env.Install("$incpath", dist_headers)
+env.Install("$parsersincpath", parsers_headers)
+env.Install("$backendsincpath", backends_headers)
+env.Install("$pkgconfigpath", "../../../libhammer.pc")
 
 testenv = env.Clone()
 testenv.ParseConfig('pkg-config --cflags --libs glib-2.0')
diff --git a/src/backends/contextfree.h b/src/backends/contextfree.h
index b387e55df21387d4be137d7ff159889de50985ba..ab04ab523064fba731d2cf292bcc1a7bd28a9faf 100644
--- a/src/backends/contextfree.h
+++ b/src/backends/contextfree.h
@@ -1,3 +1,8 @@
+/*
+ * NOTE: This is an internal header and installed for use by extensions. The
+ * API is not guaranteed stable.
+*/
+
 // This is an internal header; it provides macros to make desugaring cleaner.
 #include <assert.h>
 #include "../internal.h"
diff --git a/src/backends/llk.c b/src/backends/llk.c
index c0cf6afef75aae37c9b9479cdc44223244326ab7..2bc39daf92b371b3b22b783623442eee36053bc0 100644
--- a/src/backends/llk.c
+++ b/src/backends/llk.c
@@ -372,13 +372,13 @@ HParseResult *h_llk_parse(HAllocator* mm__, const HParser* parser, HInputStream*
 
     // perform token reshape if indicated
     if(x->reshape)
-      tok = (HParsedToken *)x->reshape(make_result(arena, tok));
+      tok = (HParsedToken *)x->reshape(make_result(arena, tok), x->user_data);
 
     // call validation and semantic action, if present
-    if(x->pred && !x->pred(make_result(tarena, tok)))
+    if(x->pred && !x->pred(make_result(tarena, tok), x->user_data))
       goto no_parse;    // validation failed -> no parse
     if(x->action)
-      tok = (HParsedToken *)x->action(make_result(arena, tok));
+      tok = (HParsedToken *)x->action(make_result(arena, tok), x->user_data);
 
     // append to result sequence
     h_carray_append(seq, tok);
diff --git a/src/backends/lr.c b/src/backends/lr.c
index d258e8a7831d11985e82d4ae76ba692e05bc6900..e7f237756361303102440700af4ceb5fcfb5abdf 100644
--- a/src/backends/lr.c
+++ b/src/backends/lr.c
@@ -307,13 +307,13 @@ bool h_lrengine_step(HLREngine *engine, const HLRAction *action)
 
     // perform token reshape if indicated
     if(symbol->reshape)
-      value = (HParsedToken *)symbol->reshape(make_result(arena, value));
+      value = (HParsedToken *)symbol->reshape(make_result(arena, value), symbol->user_data);
 
     // call validation and semantic action, if present
-    if(symbol->pred && !symbol->pred(make_result(tarena, value)))
+    if(symbol->pred && !symbol->pred(make_result(tarena, value), symbol->user_data))
       return false;     // validation failed -> no parse; terminate
     if(symbol->action)
-      value = (HParsedToken *)symbol->action(make_result(arena, value));
+      value = (HParsedToken *)symbol->action(make_result(arena, value), symbol->user_data);
 
     // this is LR, building a right-most derivation bottom-up, so no reduce can
     // follow a reduce. we can also assume no conflict follows for GLR if we
diff --git a/src/backends/regex.h b/src/backends/regex.h
index a84904d0b6bcd4ea18b8b0281b625c4c303e9a8d..4ea85a884b3fdec764f9ad94fc4c48880a0a6ea2 100644
--- a/src/backends/regex.h
+++ b/src/backends/regex.h
@@ -1,3 +1,8 @@
+/*
+ * NOTE: This is an internal header and installed for use by extensions. The
+ * API is not guaranteed stable.
+*/
+
 // Internal defs
 #ifndef HAMMER_BACKEND_REGEX__H
 #define HAMMER_BACKEND_REGEX__H
diff --git a/src/bindings/python/SConscript b/src/bindings/python/SConscript
index 0bde353e3aaa5fa9a521614e7e252c661145a925..fd03a3f3ab8f93f5f7b2c4310655c7255ffcf946 100644
--- a/src/bindings/python/SConscript
+++ b/src/bindings/python/SConscript
@@ -18,6 +18,6 @@ libhammer_python = pythonenv.SharedLibrary('hammer', swig, SHLIBPREFIX='_')
 
 pytestenv = pythonenv.Clone()
 pytestenv['ENV']['LD_LIBRARY_PATH'] = os.path.dirname(str(libhammer_shared[0]))
-pytestenv.Command(None, ['hammer_tests.py', libhammer_python], "nosetests -vv $SOURCE")
+pytestenv.Command(None, ['hammer_tests.py'] + libhammer_python, "nosetests -vv $SOURCE")
 
 Clean('.', ['hammer.pyc', 'hammer_tests.py', 'hammer_tests.pyc']) 
diff --git a/src/bindings/python/hammer_tests.py b/src/bindings/python/hammer_tests.py
index 41cd13fd3cf46e7f5e9cf9946825c9dad5022695..546c2c5dd4c9617454c8d4327cd3a896aece3de9 100644
--- a/src/bindings/python/hammer_tests.py
+++ b/src/bindings/python/hammer_tests.py
@@ -4,462 +4,461 @@ import hammer as h
 class TestTokenParser(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_token("95\xa2", 3)
+        cls.parser = h.token("95\xa2")
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "95\xa2", 3).ast.token_data.bytes, "95\xa2")
+        self.assertEqual(self.parser.parse("95\xa2"), "95\xa2")
     def test_partial_fails(self):
-        self.assertEqual(h.h_parse(self.parser, "95", 2), None)
+        self.assertEqual(self.parser.parse("95"), None)
 
 class TestChParser(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser_int = h.h_ch(0xa2)
-        cls.parser_chr = h.h_ch("\xa2")
+        cls.parser_int = h.ch(0xa2)
+        cls.parser_chr = h.ch("\xa2")
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser_int, "\xa2", 1).ast.token_data.uint, 0xa2)
-        self.assertEqual(h.h_parse(self.parser_chr, "\xa2", 1).ast.token_data.uint, ord("\xa2"))
+        self.assertEqual(self.parser_int.parse("\xa2"), 0xa2)
+        self.assertEqual(self.parser_chr.parse("\xa2"), "\xa2")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser_int, "\xa3", 1), None)
-        self.assertEqual(h.h_parse(self.parser_chr, "\xa3", 1), None)
+        self.assertEqual(self.parser_int.parse("\xa3"), None)
+        self.assertEqual(self.parser_chr.parse("\xa3"), None)
 
 class TestChRange(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_ch_range("a", "c")
+        cls.parser = h.ch_range("a", "c")
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "b", 1).ast.token_data.uint, ord("b"))
+        self.assertEqual(self.parser.parse("b"), "b")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "d", 1), None)
+        self.assertEqual(self.parser.parse("d"), None)
 
 class TestInt64(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_int64()
+        cls.parser = h.int64()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\xff\xff\xff\xfe\x00\x00\x00\x00", 8).ast.token_data.sint, -0x200000000)
+        self.assertEqual(self.parser.parse("\xff\xff\xff\xfe\x00\x00\x00\x00"), -0x200000000)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\xff\xff\xff\xfe\x00\x00\x00", 7), None)
+        self.assertEqual(self.parser.parse("\xff\xff\xff\xfe\x00\x00\x00"), None)
 
 class TestInt32(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_int32()
+        cls.parser = h.int32()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\xff\xfe\x00\x00", 4).ast.token_data.sint, -0x20000)
-        self.assertEqual(h.h_parse(self.parser, "\x00\x02\x00\x00", 4).ast.token_data.sint, 0x20000)
+        self.assertEqual(self.parser.parse("\xff\xfe\x00\x00"), -0x20000)
+        self.assertEqual(self.parser.parse("\x00\x02\x00\x00"), 0x20000)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\xff\xfe\x00", 3), None)
-        self.assertEqual(h.h_parse(self.parser, "\x00\x02\x00", 3), None)
+        self.assertEqual(self.parser.parse("\xff\xfe\x00"), None)
+        self.assertEqual(self.parser.parse("\x00\x02\x00"), None)
 
 class TestInt16(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_int16()
+        cls.parser = h.int16()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\xfe\x00", 2).ast.token_data.sint, -0x200)
-        self.assertEqual(h.h_parse(self.parser, "\x02\x00", 2).ast.token_data.sint, 0x200)
+        self.assertEqual(self.parser.parse("\xfe\x00"), -0x200)
+        self.assertEqual(self.parser.parse("\x02\x00"), 0x200)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\xfe", 1), None)
-        self.assertEqual(h.h_parse(self.parser, "\x02", 1), None)
+        self.assertEqual(self.parser.parse("\xfe"), None)
+        self.assertEqual(self.parser.parse("\x02"), None)
 
 class TestInt8(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_int8()
+        cls.parser = h.int8()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\x88", 1).ast.token_data.sint, -0x78)
+        self.assertEqual(self.parser.parse("\x88"), -0x78)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "", 0), None)
+        self.assertEqual(self.parser.parse(""), None)
 
 class TestUint64(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_uint64()
+        cls.parser = h.uint64()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\x00\x00\x00\x02\x00\x00\x00\x00", 8).ast.token_data.uint, 0x200000000)
+        self.assertEqual(self.parser.parse("\x00\x00\x00\x02\x00\x00\x00\x00"), 0x200000000)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\x00\x00\x00\x02\x00\x00\x00", 7), None)
+        self.assertEqual(self.parser.parse("\x00\x00\x00\x02\x00\x00\x00"), None)
 
 class TestUint32(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_uint32()
+        cls.parser = h.uint32()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\x00\x02\x00\x00", 4).ast.token_data.uint, 0x20000)
+        self.assertEqual(self.parser.parse("\x00\x02\x00\x00"), 0x20000)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\x00\x02\x00", 3), None)
+        self.assertEqual(self.parser.parse("\x00\x02\x00"), None)
 
 class TestUint16(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_uint16()
+        cls.parser = h.uint16()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\x02\x00", 2).ast.token_data.uint, 0x200)
+        self.assertEqual(self.parser.parse("\x02\x00"), 0x200)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\x02", 1), None)
+        self.assertEqual(self.parser.parse("\x02"), None)
 
 class TestUint8(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_uint8()
+        cls.parser = h.uint8()
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\x78", 1).ast.token_data.uint, 0x78)
+        self.assertEqual(self.parser.parse("\x78"), 0x78)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "", 0), None)
+        self.assertEqual(self.parser.parse(""), None)
         
 class TestIntRange(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_int_range(h.h_uint8(), 3, 10)
+        cls.parser = h.int_range(h.uint8(), 3, 10)
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "\x05", 1).ast.token_data.uint, 5)
+        self.assertEqual(self.parser.parse("\x05"), 5)
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "\x0b", 1), None)
+        self.assertEqual(self.parser.parse("\x0b"), None)
 
 class TestWhitespace(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_whitespace(h.h_ch("a"))
+        cls.parser = h.whitespace(h.ch("a"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1).ast.token_data.uint, ord("a"))
-        self.assertEqual(h.h_parse(self.parser, " a", 2).ast.token_data.uint, ord("a"))
-        self.assertEqual(h.h_parse(self.parser, "  a", 3).ast.token_data.uint, ord("a"))
-        self.assertEqual(h.h_parse(self.parser, "\ta", 2).ast.token_data.uint, ord("a"))
+        self.assertEqual(self.parser.parse("a"), "a")
+        self.assertEqual(self.parser.parse(" a"), "a")
+        self.assertEqual(self.parser.parse("  a"), "a")
+        self.assertEqual(self.parser.parse("\ta"), "a")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "_a", 2), None)
+        self.assertEqual(self.parser.parse("_a"), None)
 
 class TestWhitespaceEnd(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_whitespace(h.h_end_p())
+        cls.parser = h.whitespace(h.end_p())
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "", 0).ast, None) # empty string
-        self.assertEqual(h.h_parse(self.parser, "  ", 2).ast, None) # empty string
+        self.assertEqual(self.parser.parse(""), None) # empty string
+        self.assertEqual(self.parser.parse("  "), None) # empty string
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "  x", 3), None)
+        self.assertEqual(self.parser.parse("  x"), None)
 
 class TestLeft(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_left(h.h_ch("a"), h.h_ch(" "))
+        cls.parser = h.left(h.ch("a"), h.ch(" "))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "a ", 2).ast.token_data.uint, ord("a"))
+        self.assertEqual(self.parser.parse("a "), "a")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
-        self.assertEqual(h.h_parse(self.parser, " ", 1), None)
-        self.assertEqual(h.h_parse(self.parser, "ab", 2), None)
+        self.assertEqual(self.parser.parse("a"), None)
+        self.assertEqual(self.parser.parse(" "), None)
+        self.assertEqual(self.parser.parse("ab"), None)
 
 class TestRight(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_right(h.h_ch(" "), h.h_ch("a"))
+        cls.parser = h.right(h.ch(" "), h.ch("a"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, " a", 2).ast.token_data.uint, ord("a"))
+        self.assertEqual(self.parser.parse(" a"), "a")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
-        self.assertEqual(h.h_parse(self.parser, " ", 1), None)
-        self.assertEqual(h.h_parse(self.parser, "ba", 2), None)
+        self.assertEqual(self.parser.parse("a"), None)
+        self.assertEqual(self.parser.parse(" "), None)
+        self.assertEqual(self.parser.parse("ba"), None)
 
 class TestMiddle(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_middle(h.h_ch(" "), h.h_ch("a"), h.h_ch(" "))
+        cls.parser = h.middle(h.ch(" "), h.ch("a"), h.ch(" "))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, " a ", 3).ast.token_data.uint, ord("a"))
+        self.assertEqual(self.parser.parse(" a "), "a")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
-        self.assertEqual(h.h_parse(self.parser, " ", 1), None)
-        self.assertEqual(h.h_parse(self.parser, " a", 2), None)
-        self.assertEqual(h.h_parse(self.parser, "a ", 2), None)
-        self.assertEqual(h.h_parse(self.parser, " b ", 3), None)
-        self.assertEqual(h.h_parse(self.parser, "ba ", 3), None)
-        self.assertEqual(h.h_parse(self.parser, " ab", 3), None)
+        self.assertEqual(self.parser.parse("a"), None)
+        self.assertEqual(self.parser.parse(" "), None)
+        self.assertEqual(self.parser.parse(" a"), None)
+        self.assertEqual(self.parser.parse("a "), None)
+        self.assertEqual(self.parser.parse(" b "), None)
+        self.assertEqual(self.parser.parse("ba "), None)
+        self.assertEqual(self.parser.parse(" ab"), None)
 
-# class TestAction(unittest.TestCase):
-#     @classmethod
-#     def setUpClass(cls):
-#         cls.parser = h.h_action(h.h_sequence__a([h.h_choice__a([h.h_ch("a"), h.h_ch("A"), None]), h.h_choice__a([h.h_ch("b"), h.h_ch("B"), None]), None]), lambda x: [y.upper() for y in x])
-#     def test_success(self):
-#         self.assertEqual(h.h_parse(self.parser, "ab", 2).ast.token_data.seq, ["A", "B"])
-#         self.assertEqual(h.h_parse(self.parser, "AB", 2).ast.token_data.seq, ["A", "B"])
-#     def test_failure(self):
-#         self.assertEqual(h.h_parse(self.parser, "XX", 2), None)
+class TestAction(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.parser = h.action(h.sequence(h.choice(h.ch("a"), h.ch("A")),
+                                         h.choice(h.ch("b"), h.ch("B"))),
+                                lambda x: [y.upper() for y in x])
+    def test_success(self):
+        self.assertEqual(self.parser.parse("ab"), ["A", "B"])
+        self.assertEqual(self.parser.parse("AB"), ["A", "B"])
+    def test_failure(self):
+        self.assertEqual(self.parser.parse("XX"), None)
 
 class TestIn(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_in("abc", 3)
+        cls.parser = h.in_("abc")
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "b", 1).ast.token_data.uint, ord("b")) 
+        self.assertEqual(self.parser.parse("b"), "b") 
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "d", 1), None)
+        self.assertEqual(self.parser.parse("d"), None)
 
 class TestNotIn(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_not_in("abc", 3)
+        cls.parser = h.not_in("abc")
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "d", 1).ast.token_data.uint, ord("d"))
+        self.assertEqual(self.parser.parse("d"), "d")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
+        self.assertEqual(self.parser.parse("a"), None)
 
 class TestEndP(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_end_p(), None])
+        cls.parser = h.sequence(h.ch("a"), h.end_p())
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a", 1).ast.token_data.seq], [ord(y) for y in ["a"]])
+        self.assertEqual(self.parser.parse("a"), ("a",))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "aa", 2), None)
+        self.assertEqual(self.parser.parse("aa"), None)
 
 class TestNothingP(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_nothing_p()
+        cls.parser = h.nothing_p()
     def test_success(self):
         pass
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
+        self.assertEqual(self.parser.parse("a"), None)
 
 class TestSequence(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_ch("b"), None])
+        cls.parser = h.sequence(h.ch("a"), h.ch("b"))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "ab", 2).ast.token_data.seq], [ord(y) for y in ["a", "b"]])
+        self.assertEqual(self.parser.parse("ab"), ('a','b'))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
-        self.assertEqual(h.h_parse(self.parser, "b", 1), None)
+        self.assertEqual(self.parser.parse("a"), None)
+        self.assertEqual(self.parser.parse("b"), None)
 
 class TestSequenceWhitespace(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_whitespace(h.h_ch("b")), None])
+        cls.parser = h.sequence(h.ch("a"), h.whitespace(h.ch("b")))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "ab", 2).ast.token_data.seq], [ord(y) for y in ["a", "b"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a b", 3).ast.token_data.seq], [ord(y) for y in ["a", "b"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a  b", 4).ast.token_data.seq], [ord(y) for y in ["a", "b"]])
+        self.assertEqual(self.parser.parse("ab"), ('a','b'))
+        self.assertEqual(self.parser.parse("a b"), ('a','b'))
+        self.assertEqual(self.parser.parse("a  b"), ('a','b'))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a  c", 4), None)
+        self.assertEqual(self.parser.parse("a  c"), None)
 
 class TestChoice(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_choice__a([h.h_ch("a"), h.h_ch("b"), None])
+        cls.parser = h.choice(h.ch("a"), h.ch("b"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1).ast.token_data.uint, ord("a"))
-        self.assertEqual(h.h_parse(self.parser, "b", 1).ast.token_data.uint, ord("b"))
+        self.assertEqual(self.parser.parse("a"), "a")
+        self.assertEqual(self.parser.parse("b"), "b")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "c", 1), None)
+        self.assertEqual(self.parser.parse("c"), None)
 
 class TestButNot(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_butnot(h.h_ch("a"), h.h_token("ab", 2))
+        cls.parser = h.butnot(h.ch("a"), h.token("ab"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1).ast.token_data.uint, ord("a"))
-        self.assertEqual(h.h_parse(self.parser, "aa", 2).ast.token_data.uint, ord("a"))
+        self.assertEqual(self.parser.parse("a"), "a")
+        self.assertEqual(self.parser.parse("aa"), "a")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "ab", 2), None)
+        self.assertEqual(self.parser.parse("ab"), None)
 
 class TestButNotRange(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_butnot(h.h_ch_range("0", "9"), h.h_ch("6"))
+        cls.parser = h.butnot(h.ch_range("0", "9"), h.ch("6"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "4", 1).ast.token_data.uint, ord("4"))
+        self.assertEqual(self.parser.parse("4"), "4")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "6", 1), None)
+        self.assertEqual(self.parser.parse("6"), None)
 
 class TestDifference(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_difference(h.h_token("ab", 2), h.h_ch("a"))
+        cls.parser = h.difference(h.token("ab"), h.ch("a"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "ab", 2).ast.token_data.bytes, "ab")
+        self.assertEqual(self.parser.parse("ab"), "ab")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
+        self.assertEqual(self.parser.parse("a"), None)
 
 class TestXor(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_xor(h.h_ch_range("0", "6"), h.h_ch_range("5", "9"))
+        cls.parser = h.xor(h.ch_range("0", "6"), h.ch_range("5", "9"))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "0", 1).ast.token_data.uint, ord("0"))
-        self.assertEqual(h.h_parse(self.parser, "9", 1).ast.token_data.uint, ord("9"))
+        self.assertEqual(self.parser.parse("0"), "0")
+        self.assertEqual(self.parser.parse("9"), "9")
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "5", 1), None)
-        self.assertEqual(h.h_parse(self.parser, "a", 1), None)
+        self.assertEqual(self.parser.parse("5"), None)
+        self.assertEqual(self.parser.parse("a"), None)
 
 class TestMany(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_many(h.h_choice__a([h.h_ch("a"), h.h_ch("b"), None]))
+        cls.parser = h.many(h.choice(h.ch("a"), h.ch("b")))
     def test_success(self):
-        self.assertEqual(h.h_parse(self.parser, "", 0).ast.token_data.seq, [])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a", 1).ast.token_data.seq], [ord(y) for y in ["a"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "b", 1).ast.token_data.seq], [ord(y) for y in ["b"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "aabbaba", 7).ast.token_data.seq], [ord(y) for y in ["a", "a", "b", "b", "a", "b", "a"]])
+        self.assertEqual(self.parser.parse(""), ())
+        self.assertEqual(self.parser.parse("a"), ('a',))
+        self.assertEqual(self.parser.parse("b"), ('b',))
+        self.assertEqual(self.parser.parse("aabbaba"), ('a','a','b','b','a','b','a'))
     def test_failure(self):
         pass
 
 class TestMany1(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_many1(h.h_choice__a([h.h_ch("a"), h.h_ch("b"), None]))
+        cls.parser = h.many1(h.choice(h.ch("a"), h.ch("b")))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a", 1).ast.token_data.seq], [ord(y) for y in ["a"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "b", 1).ast.token_data.seq], [ord(y) for y in ["b"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "aabbaba", 7).ast.token_data.seq], [ord(y) for y in ["a", "a", "b", "b", "a", "b", "a"]])
+        self.assertEqual(self.parser.parse("a"), ("a",))
+        self.assertEqual(self.parser.parse("b"), ("b",))
+        self.assertEqual(self.parser.parse("aabbaba"), ("a", "a", "b", "b", "a", "b", "a"))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "", 0), None)
-        self.assertEqual(h.h_parse(self.parser, "daabbabadef", 11), None)
+        self.assertEqual(self.parser.parse(""), None)
+        self.assertEqual(self.parser.parse("daabbabadef"), None)
 
 class TestRepeatN(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_repeat_n(h.h_choice__a([h.h_ch("a"), h.h_ch("b"), None]), 2)
+        cls.parser = h.repeat_n(h.choice(h.ch("a"), h.ch("b")), 2)
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "abdef", 5).ast.token_data.seq], [ord(y) for y in ["a", "b"]])
+        self.assertEqual(self.parser.parse("abdef"), ('a', 'b'))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "adef", 4), None)
-        self.assertEqual(h.h_parse(self.parser, "dabdef", 5), None)
+        self.assertEqual(self.parser.parse("adef"), None)
+        self.assertEqual(self.parser.parse("dabdef"), None)
 
 class TestOptional(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_optional(h.h_choice__a([h.h_ch("b"), h.h_ch("c"), None])), h.h_ch("d"), None])
+        cls.parser = h.sequence(h.ch("a"), h.optional(h.choice(h.ch("b"), h.ch("c"))), h.ch("d"))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "abd", 3).ast.token_data.seq], [ord(y) for y in ["a", "b", "d"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "acd", 3).ast.token_data.seq], [ord(y) for y in ["a", "c", "d"]])
-        ### FIXME check this out in repl, what does tree look like
-        #self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "ad", 2).ast.token_data.seq], [ord(y)["a", None, "d"]])
+        self.assertEqual(self.parser.parse("abd"), ('a','b','d'))
+        self.assertEqual(self.parser.parse("acd"), ('a','c','d'))
+        self.assertEqual(self.parser.parse("ad"), ('a',h.Placeholder(), 'd'))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "aed", 3), None)
-        self.assertEqual(h.h_parse(self.parser, "ab", 2), None)
-        self.assertEqual(h.h_parse(self.parser, "ac", 2), None)
+        self.assertEqual(self.parser.parse("aed"), None)
+        self.assertEqual(self.parser.parse("ab"), None)
+        self.assertEqual(self.parser.parse("ac"), None)
 
 class TestIgnore(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_ignore(h.h_ch("b")), h.h_ch("c"), None])
+        cls.parser = h.sequence(h.ch("a"), h.ignore(h.ch("b")), h.ch("c"))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "abc", 3).ast.token_data.seq], [ord(y) for y in ["a", "c"]])
+        self.assertEqual(self.parser.parse("abc"), ("a","c"))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "ac", 2), None)
+        self.assertEqual(self.parser.parse("ac"), None)
 
 class TestSepBy(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sepBy(h.h_choice__a([h.h_ch("1"), h.h_ch("2"), h.h_ch("3"), None]), h.h_ch(","))
+        cls.parser = h.sepBy(h.choice(h.ch("1"), h.ch("2"), h.ch("3")), h.ch(","))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "1,2,3", 5).ast.token_data.seq], [ord(y) for y in ["1", "2", "3"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "1,3,2", 5).ast.token_data.seq], [ord(y) for y in ["1", "3", "2"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "1,3", 3).ast.token_data.seq], [ord(y) for y in ["1", "3"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "3", 1).ast.token_data.seq], [ord(y) for y in ["3"]])
-        self.assertEqual(h.h_parse(self.parser, "", 0).ast.token_data.seq, [])
+        self.assertEqual(self.parser.parse("1,2,3"), ('1','2','3'))
+        self.assertEqual(self.parser.parse("1,3,2"), ('1','3','2'))
+        self.assertEqual(self.parser.parse("1,3"), ('1','3'))
+        self.assertEqual(self.parser.parse("3"), ('3',))
+        self.assertEqual(self.parser.parse(""), ())
     def test_failure(self):
         pass
 
 class TestSepBy1(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sepBy1(h.h_choice__a([h.h_ch("1"), h.h_ch("2"), h.h_ch("3"), None]), h.h_ch(","))
+        cls.parser = h.sepBy1(h.choice(h.ch("1"), h.ch("2"), h.ch("3")), h.ch(","))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "1,2,3", 5).ast.token_data.seq], [ord(y) for y in ["1", "2", "3"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "1,3,2", 5).ast.token_data.seq], [ord(y) for y in ["1", "3", "2"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "1,3", 3).ast.token_data.seq], [ord(y) for y in ["1", "3"]])
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "3", 1).ast.token_data.seq], [ord(y) for y in ["3"]])
+        self.assertEqual(self.parser.parse("1,2,3"), ('1','2','3'))
+        self.assertEqual(self.parser.parse("1,3,2"), ('1','3','2'))
+        self.assertEqual(self.parser.parse("1,3"), ('1','3'))
+        self.assertEqual(self.parser.parse("3"), ('3',))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "", 0), None)
+        self.assertEqual(self.parser.parse(""), None)
 
-### segfaults
 class TestEpsilonP1(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_epsilon_p(), h.h_ch("b"), None])
+        cls.parser = h.sequence(h.ch("a"), h.epsilon_p(), h.ch("b"))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "ab", 2).ast.token_data.seq], [ord(y) for y in ["a", "b"]])
+        self.assertEqual(self.parser.parse("ab"), ("a", "b"))
     def test_failure(self):
         pass
 
 class TestEpsilonP2(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_epsilon_p(), h.h_ch("a"), None])
+        cls.parser = h.sequence(h.epsilon_p(), h.ch("a"))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a", 1).ast.token_data.seq], [ord(y) for y in ["a"]])
+        self.assertEqual(self.parser.parse("a"), ("a",))
     def test_failure(self):
         pass
 
 class TestEpsilonP3(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_epsilon_p(), None])
+        cls.parser = h.sequence(h.ch("a"), h.epsilon_p())
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a", 1).ast.token_data.seq], [ord(y) for y in ["a"]])
+        self.assertEqual(self.parser.parse("a"), ("a",))
     def test_failure(self):
         pass
 
-# class TestAttrBool(unittest.TestCase):
-#     @classmethod
-#     def setUpClass(cls):
-#         cls.parser = h.h_attr_bool(h.h_many1(h.h_choice__a([h.h_ch("a"), h.h_ch("b"), None])), lambda x: x[0] == x[1])
-#     def test_success(self):
-#         self.assertEqual(h.h_parse(self.parser, "aa", 2).ast.token_data.seq, ["a", "a"])
-#         self.assertEqual(h.h_parse(self.parser, "bb", 2).ast.token_data.seq, ["b", "b"])
-#     def test_failure(self):
-#         self.assertEqual(h.h_parse(self.parser, "ab", 2), None)
+class TestAttrBool(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.parser = h.attr_bool(h.many1(h.choice(h.ch("a"), h.ch("b"))),
+                                 lambda x: x[0] == x[1])
+    def test_success(self):
+        self.assertEqual(self.parser.parse("aa"), ("a", "a"))
+        self.assertEqual(self.parser.parse("bb"), ("b", "b"))
+    def test_failure(self):
+        self.assertEqual(self.parser.parse("ab"), None)
 
 class TestAnd1(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_and(h.h_ch("0")), h.h_ch("0"), None])
+        cls.parser = h.sequence(h.and_(h.ch("0")), h.ch("0"))
     def test_success(self):
-         self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "0", 1).ast.token_data.seq], [ord(y) for y in ["0"]])
+        self.assertEqual(self.parser.parse("0"), ("0",))
     def test_failure(self):
         pass
 
 class TestAnd2(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_and(h.h_ch("0")), h.h_ch("1"), None])
+        cls.parser = h.sequence(h.and_(h.ch("0")), h.ch("1"))
     def test_success(self):
         pass
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "0", 1), None)
+        self.assertEqual(self.parser.parse("0"), None)
 
 class TestAnd3(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("1"), h.h_and(h.h_ch("2")), None])
+        cls.parser = h.sequence(h.ch("1"), h.and_(h.ch("2")))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "12", 2).ast.token_data.seq], [ord(y) for y in ["1"]])
+        self.assertEqual(self.parser.parse("12"), ('1',))
     def test_failure(self):
         pass
 
 class TestNot1(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_choice__a([h.h_ch("+"), h.h_token("++", 2), None]), h.h_ch("b"), None])
+        cls.parser = h.sequence(h.ch("a"),
+                                h.choice(h.ch("+"), h.token("++")),
+                                h.ch("b"))
     def test_success(self):
-        self.assertEqual([x.token_data.uint for x in h.h_parse(self.parser, "a+b", 3).ast.token_data.seq], [ord(y) for y in ["a", "+", "b"]])
+        self.assertEqual(self.parser.parse("a+b"), ("a", "+", "b"))
     def test_failure(self):
-        self.assertEqual(h.h_parse(self.parser, "a++b", 4), None)
+        self.assertEqual(self.parser.parse("a++b"), None)
 
 class TestNot2(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_sequence__a([h.h_ch("a"), h.h_choice__a([h.h_sequence__a([h.h_ch("+"), h.h_not(h.h_ch("+")), None]), h.h_token("++", 2), None]), h.h_ch("b"), None])
+        cls.parser = h.sequence(h.ch("a"), h.choice(h.sequence(h.ch("+"), h.not_(h.ch("+"))),
+                                                    h.token("++")),
+                                h.ch("b"))
     def test_success(self):
-        tree = h.h_parse(self.parser, "a+b", 3).ast.token_data.seq
-        tree[1] = tree[1].token_data.seq[0]
-        self.assertEqual([x.token_data.uint for x in tree], [ord(y) for y in ["a", "+", "b"]])
-        tree = h.h_parse(self.parser, "a++b", 4).ast.token_data.seq
-        tree[0] = chr(tree[0].token_data.uint)
-        tree[1] = tree[1].token_data.bytes
-        tree[2] = chr(tree[2].token_data.uint)
-        self.assertEqual(tree, ["a", "++", "b"])
+        self.assertEqual(self.parser.parse("a+b"), ('a', ('+',), 'b'))
+        self.assertEqual(self.parser.parse("a++b"), ('a', "++", 'b'))
     def test_failure(self):
         pass
 
@@ -467,32 +466,29 @@ class TestNot2(unittest.TestCase):
 # #class TestLeftrec(unittest.TestCase):
 # #    @classmethod
 # #    def setUpClass(cls):
-# #        cls.parser = h.h_indirect()
-# #        a = h.h_ch("a")
-# #        h.h_bind_indirect(cls.parser, h.h_choice(h.h_sequence(cls.parser, a), a))
+# #        cls.parser = h.indirect()
+# #        a = h.ch("a")
+# #        h.bind_indirect(cls.parser, h.choice(h.sequence(cls.parser, a), a))
 # #    def test_success(self):
-# #        self.assertEqual(h.h_parse(self.parser, "a", 1).ast.token_data.bytes, "a")
-# #        self.assertEqual(h.h_parse(self.parser, "aa", 2).ast.token_data.seq, ["a", "a"])
-# #        self.assertEqual(h.h_parse(self.parser, "aaa", 3).ast.token_data.seq, ["a", "a", "a"])
+# #        self.assertEqual(self.parser.parse("a"), "a")
+# #        self.assertEqual(self.parser.parse("aa"), ["a", "a"])
+# #        self.assertEqual(self.parser.parse("aaa"), ["a", "a", "a"])
 # #    def test_failure(self):
 # #        pass
 
+
 class TestRightrec(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.parser = h.h_indirect()
-        a = h.h_ch("a")
-        h.h_bind_indirect(cls.parser, h.h_choice__a([h.h_sequence__a([a, cls.parser, None]), h.h_epsilon_p(), None]))
+        #raise unittest.SkipTest("Bind doesn't work right now")
+        cls.parser = h.indirect()
+        a = h.ch("a")
+        cls.parser.bind(h.choice(h.sequence(a, cls.parser),
+                                 h.epsilon_p()))
     def test_success(self):
-        tree = h.h_parse(self.parser, "a", 1).ast.token_data.seq
-        self.assertEqual(tree[0].token_data.uint, ord("a"))
-        tree = h.h_parse(self.parser, "aa", 2).ast.token_data.seq
-        self.assertEqual(tree[0].token_data.uint, ord("a"))
-        self.assertEqual(tree[1].token_data.seq[0].token_data.uint, ord("a"))
-        tree = h.h_parse(self.parser, "aaa", 3).ast.token_data.seq
-        self.assertEqual(tree[0].token_data.uint, ord("a"))
-        self.assertEqual(tree[1].token_data.seq[0].token_data.uint, ord("a"))
-        self.assertEqual(tree[1].token_data.seq[1].token_data.seq[0].token_data.uint, ord("a"))
+        self.assertEqual(self.parser.parse("a"), ('a',))
+        self.assertEqual(self.parser.parse("aa"), ('a', ('a',)))
+        self.assertEqual(self.parser.parse("aaa"), ('a', ('a', ('a',))))
     def test_failure(self):
         pass
 
@@ -500,15 +496,15 @@ class TestRightrec(unittest.TestCase):
 # #class TestAmbiguous(unittest.TestCase):
 # #    @classmethod
 # #    def setUpClass(cls):
-# #        cls.parser = h.h_indirect()
-# #        d = h.h_ch("d")
-# #        p = h.h_ch("+")
-# #        h.h_bind_indirect(cls.parser, h.h_choice(h.h_sequence(cls.parser, p, cls.parser), d))
+# #        cls.parser = h.indirect()
+# #        d = h.ch("d")
+# #        p = h.ch("+")
+# #        h.bind_indirect(cls.parser, h.choice(h.sequence(cls.parser, p, cls.parser), d))
 # #        # this is supposed to be flattened
 # #    def test_success(self):
-# #        self.assertEqual(h.h_parse(self.parser, "d", 1).ast.token_data.seq, ["d"])
-# #        self.assertEqual(h.h_parse(self.parser, "d+d", 3).ast.token_data.seq, ["d", "+", "d"])
-# #        self.assertEqual(h.h_parse(self.parser, "d+d+d", 5).ast.token_data.seq, ["d", "+", "d", "+", "d"])
+# #        self.assertEqual(self.parser.parse("d"), ["d"])
+# #        self.assertEqual(self.parser.parse("d+d"), ["d", "+", "d"])
+# #        self.assertEqual(self.parser.parse("d+d+d"), ["d", "+", "d", "+", "d"])
 # #    def test_failure(self):
-# #        self.assertEqual(h.h_parse(self.parser, "d+", 2), None)
+# #        self.assertEqual(self.parser.parse("d+"), None)
 
diff --git a/src/bindings/swig/hammer.i b/src/bindings/swig/hammer.i
index 81a9dd1e777f868c44abb86537b592f32a495012..5ac8c3767b2c639e2a5444de532ca1e59c8a450a 100644
--- a/src/bindings/swig/hammer.i
+++ b/src/bindings/swig/hammer.i
@@ -1,26 +1,53 @@
 %module hammer
+
 %nodefaultctor;
 
 %include "stdint.i"
- //%include "typemaps.i"
- //%apply char [ANY] { uint8_t [ANY] };
 
 #if defined(SWIGPYTHON)
 %ignore HCountedArray_;
-%typemap(in) uint8_t* {
-  Py_INCREF($input);
-  $1 = (uint8_t*)PyString_AsString($input);
- }
-%typemap(out) uint8_t* {
-  $result = PyString_FromString((char*)$1);
+%apply (char *STRING, size_t LENGTH) {(uint8_t* str, size_t len)}
+%apply (uint8_t* str, size_t len) {(const uint8_t* input, size_t length)}
+%apply (uint8_t* str, size_t len) {(const uint8_t* str, const size_t len)}
+%apply (uint8_t* str, size_t len) {(const uint8_t* charset, size_t length)}
+
+
+%rename("_%s") "";
+// %rename(_h_ch) h_ch;
+
+%inline {
+  static PyObject *_helper_Placeholder = NULL, *_helper_ParseError = NULL;
+
+  static void register_helpers(PyObject* parse_error, PyObject *placeholder) {
+    _helper_ParseError = parse_error;
+    _helper_Placeholder = placeholder;
+  }
  }
+
+%pythoncode %{
+  class Placeholder(object):
+      """The python equivalent of TT_NONE"""
+      def __str__(self):
+          return "Placeholder"
+      def __repr__(self):
+          return "Placeholder"
+      def __eq__(self, other):
+          return type(self) == type(other)
+  class ParseError(Exception):
+      """The parse failed; the message may have more information"""
+      pass
+
+  _hammer._register_helpers(ParseError,
+			    Placeholder)
+  %}
+
 %typemap(in) void*[] {
   if (PyList_Check($input)) {
     Py_INCREF($input);
     int size = PyList_Size($input);
     int i = 0;
     int res = 0;
-    $1 = (void**)malloc(size*sizeof(HParser*));
+    $1 = (void**)malloc((size+1)*sizeof(HParser*));
     for (i=0; i<size; i++) {
       PyObject *o = PyList_GetItem($input, i);
       res = SWIG_ConvertPtr(o, &($1[i]), SWIGTYPE_p_HParser_, 0 | 0);
@@ -28,6 +55,7 @@
 	SWIG_exception_fail(SWIG_ArgError(res), "that wasn't an HParser" );
       }
     }
+    $1[size] = NULL;
   } else {
     PyErr_SetString(PyExc_TypeError, "__a functions take lists of parsers as their argument");
     return NULL;
@@ -56,6 +84,49 @@
     PyList_SetItem($result, i, o);
   }
  }
+%typemap(out) struct HParseResult_* {
+  if ($1 == NULL) {
+    // TODO: raise parse failure
+    Py_INCREF(Py_None);
+    $result = Py_None;
+  } else {
+    $result = hpt_to_python($1->ast);
+  }
+ }
+%typemap(newfree) struct HParseResult_* {
+  h_parse_result_free($input);
+ }
+%inline %{
+  static int h_tt_python;
+  %}
+%init %{
+  h_tt_python = h_allocate_token_type("com.upstandinghackers.hammer.python");
+  %}
+
+
+
+
+%typemap(in) (HPredicate pred, void* user_data) {
+  Py_INCREF($input);
+  $2 = $input;
+  $1 = call_predicate;
+ }
+
+%typemap(in) (const HAction a, void* user_data) {
+  Py_INCREF($input);
+  $2 = $input;
+  $1 = call_action;
+ }
+
+%inline %{
+
+  struct HParsedToken_;
+  struct HParseResult_;
+  static PyObject* hpt_to_python(const struct HParsedToken_ *token);
+  
+  static struct HParsedToken_* call_action(const struct HParseResult_ *p, void* user_data);
+  static int call_predicate(const struct HParseResult_ *p, void* user_data);
+ %}
 #else
   #warning no uint8_t* typemaps defined
 #endif
@@ -65,7 +136,208 @@
 #include "allocator.h"
 #include "hammer.h"
 #include "internal.h"
+#include "glue.h"
 %}
 %include "allocator.h"
 %include "hammer.h"
 
+%extend HArena_ {
+  ~HArena_() {
+    h_delete_arena($self);
+  }
+ };
+%extend HParseResult_ {
+  ~HParseResult_() {
+    h_parse_result_free($self);
+  }
+};
+
+%newobject h_parse;
+%delobject h_parse_result_free;
+%newobject h_new_arena;
+%delobject h_delete_arena;
+
+#ifdef SWIGPYTHON
+%inline {
+  static PyObject* hpt_to_python(const HParsedToken *token) {
+    // Caller holds a reference to returned object
+    PyObject *ret;
+    if (token == NULL) {
+      Py_RETURN_NONE;
+    }
+    switch (token->token_type) {
+    case TT_NONE:
+      return PyObject_CallFunctionObjArgs(_helper_Placeholder, NULL);
+      break;
+    case TT_BYTES:
+      return PyString_FromStringAndSize((char*)token->token_data.bytes.token, token->token_data.bytes.len);
+    case TT_SINT:
+      // TODO: return PyINT if appropriate
+      return PyLong_FromLong(token->token_data.sint);
+    case TT_UINT:
+      // TODO: return PyINT if appropriate
+      return PyLong_FromUnsignedLong(token->token_data.uint);
+    case TT_SEQUENCE:
+      ret = PyTuple_New(token->token_data.seq->used);
+      for (int i = 0; i < token->token_data.seq->used; i++) {
+	PyTuple_SET_ITEM(ret, i, hpt_to_python(token->token_data.seq->elements[i]));
+      }
+      return ret;
+    default:
+      if (token->token_type == h_tt_python) {
+	ret = (PyObject*)token->token_data.user;
+	Py_INCREF(ret);
+	return ret;
+      } else {
+	return SWIG_NewPointerObj((void*)token, SWIGTYPE_p_HParsedToken_, 0 | 0);
+	// TODO: support registry
+      }
+      
+    }
+  }
+  static struct HParsedToken_* call_action(const struct HParseResult_ *p, void* user_data) {
+    PyObject *callable = user_data;
+    PyObject *ret = PyObject_CallFunctionObjArgs(callable,
+						 hpt_to_python(p->ast),
+						 NULL);
+    if (ret == NULL) {
+      PyErr_Print();
+      assert(ret != NULL);
+    }	
+    // TODO: add reference to ret to parse-local data
+    // For now, just hold onto reference
+    HParsedToken *tok = h_make(p->arena, h_tt_python, ret);
+    return tok;
+   }
+  
+  static int call_predicate(const struct HParseResult_ *p, void* user_data) {
+    PyObject *callable = user_data;
+    PyObject *ret = PyObject_CallFunctionObjArgs(callable,
+						 hpt_to_python(p->ast),
+						 NULL);
+    int rret = 0;
+    if (ret == NULL) {
+      // TODO: throw exception
+      PyErr_Print();
+      assert(ret != NULL);
+    }	
+    // TODO: add reference to ret to parse-local data
+    rret = PyObject_IsTrue(ret);
+    Py_DECREF(ret);
+    return rret;
+  }
+  
+ }
+
+%rename("%s") "";
+
+%extend HParser_ {
+    HParseResult* parse(const uint8_t* input, size_t length) {
+        return h_parse($self, input, length);
+    }
+    bool compile(HParserBackend backend) {
+        return h_compile($self, backend, NULL) == 0;
+    }
+    PyObject* __dir__() {
+        PyObject* ret = PyList_New(2);
+        PyList_SET_ITEM(ret, 0, PyString_FromString("parse"));
+        PyList_SET_ITEM(ret, 1, PyString_FromString("compile"));
+        return ret;
+    }
+}
+
+%pythoncode %{
+
+def action(p, act):
+    return _h_action(p, act)
+def attr_bool(p, pred):
+    return _h_attr_bool(p, pred)
+
+def ch(ch):
+    if isinstance(ch, str) or isinstance(ch, unicode):
+        return token(ch)
+    else:
+        return  _h_ch(ch)
+
+def ch_range(c1, c2):
+    dostr = isinstance(c1, str)
+    dostr2 = isinstance(c2, str)
+    if isinstance(c1, unicode) or isinstance(c2, unicode):
+        raise TypeError("ch_range only works on bytes")
+    if dostr != dostr2:
+        raise TypeError("Both arguments to ch_range must be the same type")
+    if dostr:
+        return action(_h_ch_range(c1, c2), chr)
+    else:
+        return _h_ch_range(c1, c2)
+def epsilon_p(): return _h_epsilon_p()
+def end_p():
+    return _h_end_p()
+def in_(charset):
+    return action(_h_in(charset), chr)
+def not_in(charset):
+    return action(_h_not_in(charset), chr)
+def not_(p): return _h_not(p)
+def int_range(p, i1, i2):
+    return _h_int_range(p, i1, i2)
+def token(string):
+    return _h_token(string)
+def whitespace(p):
+    return _h_whitespace(p)
+def xor(p1, p2):
+    return _h_xor(p1, p2)
+def butnot(p1, p2):
+    return _h_butnot(p1, p2)
+def and_(p1):
+    return _h_and(p1)
+def difference(p1, p2):
+    return _h_difference(p1, p2)
+
+def sepBy(p, sep): return _h_sepBy(p, sep)
+def sepBy1(p, sep): return _h_sepBy1(p, sep)
+def many(p): return _h_many(p)
+def many1(p): return _h_many1(p)
+def repeat_n(p, n): return _h_repeat_n(p, n)
+def choice(*args): return _h_choice__a(list(args))
+def sequence(*args): return _h_sequence__a(list(args))
+
+def optional(p): return _h_optional(p)
+def nothing_p(): return _h_nothing_p()
+def ignore(p): return _h_ignore(p)
+
+def left(p1, p2): return _h_left(p1, p2)
+def middle(p1, p2, p3): return _h_middle(p1, p2, p3)
+def right(p1, p2): return _h_right(p1, p2)
+
+   
+class HIndirectParser(_HParser_):
+    def __init__(self):
+        # Shoves the guts of an _HParser_ into a HIndirectParser.
+        tret = _h_indirect()
+        self.__dict__.clear()
+        self.__dict__.update(tret.__dict__)
+        
+    def __dir__(self):
+        return super(HIndirectParser, self).__dir__() + ['bind']
+    def bind(self, parser):
+        _h_bind_indirect(self, parser)
+
+def indirect():
+    return HIndirectParser()
+
+def bind_indirect(indirect, new_parser):
+    indirect.bind(new_parser)
+
+def uint8():  return _h_uint8()
+def uint16(): return _h_uint16()
+def uint32(): return _h_uint32()
+def uint64(): return _h_uint64()
+def int8():  return _h_int8()
+def int16(): return _h_int16()
+def int32(): return _h_int32()
+def int64(): return _h_int64()
+
+
+%}
+
+#endif
diff --git a/src/glue.c b/src/glue.c
index 5e3804d0e0ec266cf3185867c975dada86f785dc..c2d915aeaab8e8d58646569f33edc5402af43023 100644
--- a/src/glue.c
+++ b/src/glue.c
@@ -5,7 +5,7 @@
 #include "parsers/parser_internal.h"
 
 // Helper to build HAction's that pick one index out of a sequence.
-HParsedToken *h_act_index(int i, const HParseResult *p)
+HParsedToken *h_act_index(int i, const HParseResult *p, void* user_data)
 {
     if(!p) return NULL;
 
@@ -23,7 +23,7 @@ HParsedToken *h_act_index(int i, const HParseResult *p)
         return tok->seq->elements[i];
 }
 
-HParsedToken *h_act_first(const HParseResult *p) {
+HParsedToken *h_act_first(const HParseResult *p, void* user_data) {
   assert(p->ast);
   assert(p->ast->token_type == TT_SEQUENCE);
   assert(p->ast->seq->used > 0);
@@ -31,7 +31,7 @@ HParsedToken *h_act_first(const HParseResult *p) {
   return p->ast->seq->elements[0];
 }
 
-HParsedToken *h_act_second(const HParseResult *p) {
+HParsedToken *h_act_second(const HParseResult *p, void* user_data) {
   assert(p->ast);
   assert(p->ast->token_type == TT_SEQUENCE);
   assert(p->ast->seq->used > 0);
@@ -39,7 +39,7 @@ HParsedToken *h_act_second(const HParseResult *p) {
   return p->ast->seq->elements[1];
 }
 
-HParsedToken *h_act_last(const HParseResult *p) {
+HParsedToken *h_act_last(const HParseResult *p, void* user_data) {
   assert(p->ast);
   assert(p->ast->token_type == TT_SEQUENCE);
   assert(p->ast->seq->used > 0);
@@ -59,7 +59,7 @@ static void act_flatten_(HCountedArray *seq, const HParsedToken *tok) {
   }
 }
 
-HParsedToken *h_act_flatten(const HParseResult *p) {
+HParsedToken *h_act_flatten(const HParseResult *p, void* user_data) {
   HCountedArray *seq = h_carray_new(p->arena);
 
   act_flatten_(seq, p->ast);
@@ -72,7 +72,7 @@ HParsedToken *h_act_flatten(const HParseResult *p) {
   return res;
 }
 
-HParsedToken *h_act_ignore(const HParseResult *p) {
+HParsedToken *h_act_ignore(const HParseResult *p, void* user_data) {
   return NULL;
 }
 
diff --git a/src/glue.h b/src/glue.h
index 54b598507927b656f9bd1d17a363cd3a7bd723ac..1fe6ce46f453e911339e5ea3090e2436283f106a 100644
--- a/src/glue.h
+++ b/src/glue.h
@@ -53,16 +53,27 @@
 // H_AVRULE is like H_VARULE but the action is attached outside the validation,
 // i.e. the validation receives the uninterpreted AST as input.
 //
-
+// H_ADRULE, H_VDRULE, H_AVDRULE, and H_VADRULE are the same as the
+// equivalent non-D variants, except that they also allow you to uset
+// the user_data pointer.  In cases where both an attr_bool and an
+// action are used, the same userdata pointer is given to both.
 
 #define H_RULE(rule, def)  HParser *rule = def
-#define H_ARULE(rule, def) HParser *rule = h_action(def, act_ ## rule)
+#define H_ARULE(rule, def) HParser *rule = h_action(def, act_ ## rule, NULL)
 #define H_VRULE(rule, def) HParser *rule = \
-  h_attr_bool(def, validate_ ## rule)
+    h_attr_bool(def, validate_ ## rule, NULL)
 #define H_VARULE(rule, def) HParser *rule = \
-  h_attr_bool(h_action(def, act_ ## rule), validate_ ## rule)
+    h_attr_bool(h_action(def, act_ ## rule, NULL), validate_ ## rule, NULL)
 #define H_AVRULE(rule, def) HParser *rule = \
-  h_action(h_attr_bool(def, validate_ ## rule), act_ ## rule)
+    h_action(h_attr_bool(def, validate_ ## rule, NULL), act_ ## rule, NULL)
+#define H_ADRULE(rule, def, data) HParser *rule =	\
+    h_action(def, act_ ## rule, data)
+#define H_VDRULE(rule, def, data) HParser *rule =	\
+    h_attr_bool(def, validate_ ## rule, data)
+#define H_VADRULE(rule, def, data) HParser *rule =		\
+    h_attr_bool(h_action(def, act_ ## rule, data), validate_ ## rule, data)
+#define H_AVDRULE(rule, def, data) HParser *rule =		\
+    h_action(h_attr_bool(def, validate_ ## rule, data), act_ ## rule, data)
 
 
 //
@@ -88,18 +99,18 @@
 // action such as h_act_index.
 //
 
-HParsedToken *h_act_index(int i, const HParseResult *p);
-HParsedToken *h_act_first(const HParseResult *p);
-HParsedToken *h_act_second(const HParseResult *p);
-HParsedToken *h_act_last(const HParseResult *p);
-HParsedToken *h_act_flatten(const HParseResult *p);
-HParsedToken *h_act_ignore(const HParseResult *p);
+HParsedToken *h_act_index(int i, const HParseResult *p, void* user_data);
+HParsedToken *h_act_first(const HParseResult *p, void* user_data);
+HParsedToken *h_act_second(const HParseResult *p, void* user_data);
+HParsedToken *h_act_last(const HParseResult *p, void* user_data);
+HParsedToken *h_act_flatten(const HParseResult *p, void* user_data);
+HParsedToken *h_act_ignore(const HParseResult *p, void* user_data);
 
 // Define 'myaction' as a specialization of 'paction' by supplying the leading
 // parameters.
 #define H_ACT_APPLY(myaction, paction, ...) \
-  HParsedToken *myaction(const HParseResult *p) { \
-    return paction(__VA_ARGS__, p); \
+  HParsedToken *myaction(const HParseResult *p, void* user_data) {	\
+    return paction(__VA_ARGS__, p, user_data);				\
   }
 
 
diff --git a/src/hammer.h b/src/hammer.h
index b4fc823dfc22bdb3ab6205e2071f556931c9ad3e..6756c0cc584951c905b9abdc918d5587b3ced28e 100644
--- a/src/hammer.h
+++ b/src/hammer.h
@@ -137,14 +137,14 @@ typedef struct HBitWriter_ HBitWriter;
  * say, structs) and stuff values for them into the void* in the 
  * tagged union in HParsedToken. 
  */
-typedef HParsedToken* (*HAction)(const HParseResult *p);
+typedef HParsedToken* (*HAction)(const HParseResult *p, void* user_data);
 
 /**
  * Type of a boolean attribute-checking function, used in the 
  * attr_bool() parser. It can be any (user-defined) function that takes
  * a HParseResult* and returns true or false. 
  */
-typedef bool (*HPredicate)(HParseResult *p);
+typedef bool (*HPredicate)(HParseResult *p, void* user_data);
 
 typedef struct HCFChoice_ HCFChoice;
 typedef struct HRVMProg_ HRVMProg;
@@ -385,7 +385,7 @@ HAMMER_FN_DECL(HParser*, h_middle, const HParser* p, const HParser* x, const HPa
  *
  * Result token type: any
  */
-HAMMER_FN_DECL(HParser*, h_action, const HParser* p, const HAction a);
+HAMMER_FN_DECL(HParser*, h_action, const HParser* p, const HAction a, void* user_data);
 
 /**
  * Parse a single character in the given charset. 
@@ -551,7 +551,7 @@ HAMMER_FN_DECL(HParser*, h_length_value, const HParser* length, const HParser* v
  * 
  * Result token type: p's result type if pred succeeded, NULL otherwise.
  */
-HAMMER_FN_DECL(HParser*, h_attr_bool, const HParser* p, HPredicate pred);
+HAMMER_FN_DECL(HParser*, h_attr_bool, const HParser* p, HPredicate pred, void* user_data);
 
 /**
  * The 'and' parser asserts that a conditional syntax is satisfied, 
@@ -657,11 +657,11 @@ void h_bit_writer_free(HBitWriter* w);
 
 // General-purpose actions for use with h_action
 // XXX to be consolidated with glue.h when merged upstream
-HParsedToken *h_act_first(const HParseResult *p);
-HParsedToken *h_act_second(const HParseResult *p);
-HParsedToken *h_act_last(const HParseResult *p);
-HParsedToken *h_act_flatten(const HParseResult *p);
-HParsedToken *h_act_ignore(const HParseResult *p);
+HParsedToken *h_act_first(const HParseResult *p, void* userdata);
+HParsedToken *h_act_second(const HParseResult *p, void* userdata);
+HParsedToken *h_act_last(const HParseResult *p, void* userdata);
+HParsedToken *h_act_flatten(const HParseResult *p, void* userdata);
+HParsedToken *h_act_ignore(const HParseResult *p, void* userdata);
 
 // {{{ Benchmark functions
 HAMMER_FN_DECL(HBenchmarkResults *, h_benchmark, HParser* parser, HParserTestcase* testcases);
@@ -669,6 +669,17 @@ void h_benchmark_report(FILE* stream, HBenchmarkResults* results);
 //void h_benchmark_dump_optimized_code(FILE* stream, HBenchmarkResults* results);
 // }}}
 
+// {{{ Token type registry
+/// Allocate a new, unused (as far as this function knows) token type.
+int h_allocate_token_type(const char* name);
+
+/// Get the token type associated with name. Returns -1 if name is unkown
+int h_get_token_type_number(const char* name);
+
+/// Get the name associated with token_type. Returns NULL if the token type is unkown
+const char* h_get_token_type_name(int token_type);
+// }}}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/internal.h b/src/internal.h
index c402da511fe75da9a4365266207634fbdc9e8798..3c639d02fcb7c1b949f8285e03ef25020dc0a1f4 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -15,6 +15,11 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
+/*
+ * NOTE: This is an internal header and installed for use by extensions. The
+ * API is not guaranteed stable.
+*/
+
 #ifndef HAMMER_INTERNAL__H
 #define HAMMER_INTERNAL__H
 #include <stdint.h>
@@ -360,6 +365,7 @@ struct HCFChoice_ {
                     // to execute before action and pred are applied.
   HAction action;
   HPredicate pred;
+  void* user_data;
 };
 
 struct HCFSequence_ {
diff --git a/src/parsers/action.c b/src/parsers/action.c
index 52c9bc1e9fdb12c0274f350d546dcde4a73036f6..e254a894320099d930e6fe08ddaa30e8d39ff18c 100644
--- a/src/parsers/action.c
+++ b/src/parsers/action.c
@@ -4,6 +4,7 @@
 typedef struct {
   const HParser *p;
   HAction action;
+  void* user_data;
 } HParseAction;
 
 static HParseResult* parse_action(void *env, HParseState *state) {
@@ -12,8 +13,8 @@ static HParseResult* parse_action(void *env, HParseState *state) {
     HParseResult *tmp = h_do_parse(a->p, state);
     //HParsedToken *tok = a->action(h_do_parse(a->p, state));
     if(tmp) {
-        const HParsedToken *tok = a->action(tmp);
-        return make_result(state->arena, (HParsedToken*)tok);
+      const HParsedToken *tok = a->action(tmp, a->user_data);
+      return make_result(state->arena, (HParsedToken*)tok);
     } else
       return NULL;
   } else // either the parser's missing or the action's missing
@@ -27,6 +28,7 @@ static void desugar_action(HAllocator *mm__, HCFStack *stk__, void *env) {
     HCFS_BEGIN_SEQ() {
       HCFS_DESUGAR(a->p);
     } HCFS_END_SEQ();
+    HCFS_THIS_CHOICE->user_data = a->user_data;
     HCFS_THIS_CHOICE->action = a->action;
     HCFS_THIS_CHOICE->reshape = h_act_first;
   } HCFS_END_CHOICE();
@@ -44,7 +46,7 @@ static bool action_isValidCF(void *env) {
 
 static bool h_svm_action_action(HArena *arena, HSVMContext *ctx, void* arg) {
   HParseResult res;
-  HAction action = arg;
+  HParseAction *a = arg;
   assert(ctx->stack_count >= 1);
   if (ctx->stack[ctx->stack_count-1]->token_type != TT_MARK) {
     assert(ctx->stack_count >= 2 && ctx->stack[ctx->stack_count-2]->token_type == TT_MARK);
@@ -56,7 +58,7 @@ static bool h_svm_action_action(HArena *arena, HSVMContext *ctx, void* arg) {
   }
   res.arena = arena;
 
-  HParsedToken *tok = action(&res);
+  HParsedToken *tok = a->action(&res, a->user_data);
   if (tok != NULL)
     ctx->stack[ctx->stack_count-1] = tok;
   else
@@ -69,7 +71,7 @@ static bool action_ctrvm(HRVMProg *prog, void* env) {
   h_rvm_insert_insn(prog, RVM_PUSH, 0);
   if (!h_compile_regex(prog, a->p))
     return false;
-  h_rvm_insert_insn(prog, RVM_ACTION, h_rvm_create_action(prog, h_svm_action_action, a->action));
+  h_rvm_insert_insn(prog, RVM_ACTION, h_rvm_create_action(prog, h_svm_action_action, a));
   return true;
 }
 
@@ -81,13 +83,14 @@ static const HParserVtable action_vt = {
   .compile_to_rvm = action_ctrvm,
 };
 
-HParser* h_action(const HParser* p, const HAction a) {
-  return h_action__m(&system_allocator, p, a);
+HParser* h_action(const HParser* p, const HAction a, void* user_data) {
+  return h_action__m(&system_allocator, p, a, user_data);
 }
 
-HParser* h_action__m(HAllocator* mm__, const HParser* p, const HAction a) {
+HParser* h_action__m(HAllocator* mm__, const HParser* p, const HAction a, void* user_data) {
   HParseAction *env = h_new(HParseAction, 1);
   env->p = p;
   env->action = a;
+  env->user_data = user_data;
   return h_new_parser(mm__, &action_vt, env);
 }
diff --git a/src/parsers/attr_bool.c b/src/parsers/attr_bool.c
index fc980b24f8eaff2fbf29da79cc630ac0a6cdd988..e8359ab03e06e681061dd75788d6ca6bb6e9b89b 100644
--- a/src/parsers/attr_bool.c
+++ b/src/parsers/attr_bool.c
@@ -4,13 +4,14 @@
 typedef struct {
   const HParser *p;
   HPredicate pred;
+  void* user_data;
 } HAttrBool;
 
 static HParseResult* parse_attr_bool(void *env, HParseState *state) {
   HAttrBool *a = (HAttrBool*)env;
   HParseResult *res = h_do_parse(a->p, state);
   if (res && res->ast) {
-    if (a->pred(res))
+    if (a->pred(res, a->user_data))
       return res;
     else
       return NULL;
@@ -42,12 +43,13 @@ static void desugar_ab(HAllocator *mm__, HCFStack *stk__, void *env) {
     } HCFS_END_SEQ();
     HCFS_THIS_CHOICE->pred = a->pred;
     HCFS_THIS_CHOICE->reshape = h_act_first;
+    HCFS_THIS_CHOICE->user_data = a->user_data;
   } HCFS_END_CHOICE();
 }
 
 static bool h_svm_action_attr_bool(HArena *arena, HSVMContext *ctx, void* arg) {
   HParseResult res;
-  HPredicate pred = arg;
+  HAttrBool *ab = arg;
   assert(ctx->stack_count >= 1);
   if (ctx->stack[ctx->stack_count-1]->token_type != TT_MARK) {
     assert(ctx->stack_count >= 2 && ctx->stack[ctx->stack_count-2]->token_type == TT_MARK);
@@ -59,7 +61,7 @@ static bool h_svm_action_attr_bool(HArena *arena, HSVMContext *ctx, void* arg) {
     res.ast = NULL;
   }
   res.arena = arena;
-  return pred(&res);
+  return ab->pred(&res, ab->user_data);
 }
 
 static bool ab_ctrvm(HRVMProg *prog, void *env) {
@@ -67,7 +69,7 @@ static bool ab_ctrvm(HRVMProg *prog, void *env) {
   h_rvm_insert_insn(prog, RVM_PUSH, 0);
   if (!h_compile_regex(prog, ab->p))
     return false;
-  h_rvm_insert_insn(prog, RVM_ACTION, h_rvm_create_action(prog, h_svm_action_attr_bool, ab->pred));
+  h_rvm_insert_insn(prog, RVM_ACTION, h_rvm_create_action(prog, h_svm_action_attr_bool, ab));
   return true;
 }
 
@@ -80,12 +82,13 @@ static const HParserVtable attr_bool_vt = {
 };
 
 
-HParser* h_attr_bool(const HParser* p, HPredicate pred) {
-  return h_attr_bool__m(&system_allocator, p, pred);
+HParser* h_attr_bool(const HParser* p, HPredicate pred, void* user_data) {
+  return h_attr_bool__m(&system_allocator, p, pred, user_data);
 }
-HParser* h_attr_bool__m(HAllocator* mm__, const HParser* p, HPredicate pred) { 
+HParser* h_attr_bool__m(HAllocator* mm__, const HParser* p, HPredicate pred, void* user_data) { 
   HAttrBool *env = h_new(HAttrBool, 1);
   env->p = p;
   env->pred = pred;
+  env->user_data = user_data;
   return h_new_parser(mm__, &attr_bool_vt, env);
 }
diff --git a/src/parsers/bits.c b/src/parsers/bits.c
index 93b4aef60e9bac7f5fa112d3087192197d3dd0ca..716524ce61a0a35cb0f9581646f72a0efa491c7f 100644
--- a/src/parsers/bits.c
+++ b/src/parsers/bits.c
@@ -17,7 +17,9 @@ static HParseResult* parse_bits(void* env, HParseState *state) {
   return make_result(state->arena, result);
 }
 
-static HParsedToken *reshape_bits(const HParseResult *p, bool signedp) {
+static HParsedToken *reshape_bits(const HParseResult *p, void* signedp_p) {
+  // signedp == NULL iff unsigned
+  bool signedp = (signedp_p != NULL);
   // XXX works only for whole bytes
   // XXX assumes big-endian
   assert(p->ast);
@@ -45,12 +47,6 @@ static HParsedToken *reshape_bits(const HParseResult *p, bool signedp) {
 
   return ret;
 }
-static HParsedToken *reshape_bits_unsigned(const HParseResult *p) {
-  return reshape_bits(p, false);
-}
-static HParsedToken *reshape_bits_signed(const HParseResult *p) {
-  return reshape_bits(p, true);
-}
 
 static void desugar_bits(HAllocator *mm__, HCFStack *stk__, void *env) {
   struct bits_env *bits = (struct bits_env*)env;
@@ -67,9 +63,9 @@ static void desugar_bits(HAllocator *mm__, HCFStack *stk__, void *env) {
 	HCFS_ADD_CHARSET(match_all);
       }
     } HCFS_END_SEQ();
-    HCFS_THIS_CHOICE->reshape = bits->signedp
-      ? reshape_bits_signed
-      : reshape_bits_unsigned;
+    HCFS_THIS_CHOICE->reshape = reshape_bits;
+    HCFS_THIS_CHOICE->user_data = bits->signedp ? HCFS_THIS_CHOICE : NULL; // HCFS_THIS_CHOICE is an arbitrary non-null pointer
+    
   } HCFS_END_CHOICE();
 }
 
diff --git a/src/parsers/optional.c b/src/parsers/optional.c
index c4282a914fb81ae82b1b2ec18bd5d91ec001b5c3..ff9fc15bbf465bd36a0edd4fd1906c1f6077c1b1 100644
--- a/src/parsers/optional.c
+++ b/src/parsers/optional.c
@@ -22,7 +22,7 @@ static bool opt_isValidCF(void *env) {
   return p->vtable->isValidCF(p->env);
 }
 
-static HParsedToken* reshape_optional(const HParseResult *p) {
+static HParsedToken* reshape_optional(const HParseResult *p, void* user_data) {
   assert(p->ast);
   assert(p->ast->token_type == TT_SEQUENCE);
 
@@ -52,6 +52,7 @@ static void desugar_optional(HAllocator *mm__, HCFStack *stk__, void *env) {
     HCFS_BEGIN_SEQ() {
     } HCFS_END_SEQ();
     HCFS_THIS_CHOICE->reshape = reshape_optional;
+    HCFS_THIS_CHOICE->user_data = NULL;
   } HCFS_END_CHOICE();
 }
 
diff --git a/src/parsers/parser_internal.h b/src/parsers/parser_internal.h
index aeb202bf410a53b262e87cc3eadde603b9e11e8a..ec97dd1b0696fcb69f4a17bfc7d4078138f4d355 100644
--- a/src/parsers/parser_internal.h
+++ b/src/parsers/parser_internal.h
@@ -1,3 +1,8 @@
+/*
+ * NOTE: This is an internal header and installed for use by extensions. The
+ * API is not guaranteed stable.
+*/
+
 #ifndef HAMMER_PARSE_INTERNAL__H
 #define HAMMER_PARSE_INTERNAL__H
 #include "../hammer.h"
diff --git a/src/parsers/sequence.c b/src/parsers/sequence.c
index bdea8c02a45c4346a7523de97a7f6238ba12c246..42c0913d91e16c973299506976ddd882e993b957 100644
--- a/src/parsers/sequence.c
+++ b/src/parsers/sequence.c
@@ -43,7 +43,7 @@ static bool sequence_isValidCF(void *env) {
   return true;
 }
 
-static HParsedToken *reshape_sequence(const HParseResult *p) {
+static HParsedToken *reshape_sequence(const HParseResult *p, void* user_data) {
   assert(p->ast);
   assert(p->ast->token_type == TT_SEQUENCE);
 
@@ -72,6 +72,7 @@ static void desugar_sequence(HAllocator *mm__, HCFStack *stk__, void *env) {
 	HCFS_DESUGAR(s->p_array[i]);
     } HCFS_END_SEQ();
     HCFS_THIS_CHOICE->reshape = reshape_sequence;
+    HCFS_THIS_CHOICE->user_data = NULL;
   } HCFS_END_CHOICE();
 }
 
diff --git a/src/parsers/token.c b/src/parsers/token.c
index 7a05636383035b9d5d50ebe191f7da35d9f10a2b..d36ec54be4c07a35b729da71455c5bc3b3555cbc 100644
--- a/src/parsers/token.c
+++ b/src/parsers/token.c
@@ -20,7 +20,7 @@ static HParseResult* parse_token(void *env, HParseState *state) {
 }
 
 
-static HParsedToken *reshape_token(const HParseResult *p) {
+static HParsedToken *reshape_token(const HParseResult *p, void* user_data) {
   // fetch sequence of uints from p
   assert(p->ast);
   assert(p->ast->token_type == TT_SEQUENCE);
@@ -52,6 +52,7 @@ static void desugar_token(HAllocator *mm__, HCFStack *stk__, void *env) {
 	HCFS_ADD_CHAR(tok->str[i]);
     } HCFS_END_SEQ();
     HCFS_THIS_CHOICE->reshape = reshape_token;
+    HCFS_THIS_CHOICE->user_data = NULL;
   } HCFS_END_CHOICE();
 }
 
diff --git a/src/registry.c b/src/registry.c
new file mode 100644
index 0000000000000000000000000000000000000000..c59b6ea9f6e0214c279d51b3997b5770278928bc
--- /dev/null
+++ b/src/registry.c
@@ -0,0 +1,87 @@
+/* Parser combinators for binary formats.
+ * Copyright (C) 2012  Meredith L. Patterson, Dan "TQ" Hirsch
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include <search.h>
+#include <stdlib.h>
+#include "hammer.h"
+#include "internal.h"
+
+typedef struct Entry_ {
+  const char* name;
+  int value;
+} Entry;
+
+static void *tt_registry = NULL;
+static Entry** tt_by_id = NULL;
+static int tt_by_id_sz = 0;
+#define TT_START TT_USER
+static int tt_next = TT_START;
+
+/*
+  // TODO: These are for the extension registry, which does not yet have a good name.
+static void *ext_registry = NULL;
+static Entry** ext_by_id = NULL;
+static int ext_by_id_sz = 0;
+static int ext_next = 0;
+*/
+
+
+static int compare_entries(const void* v1, const void* v2) {
+  const Entry *e1 = (Entry*)v1, *e2 = (Entry*)v2;
+  return strcmp(e1->name, e2->name);
+}
+
+int h_allocate_token_type(const char* name) {
+  Entry* new_entry = malloc(sizeof(*new_entry));
+  new_entry->name = name;
+  new_entry->value = -1;
+  Entry* probe = *(Entry**)tsearch(new_entry, &tt_registry, compare_entries);
+  if (probe->value != -1) {
+    // Token type already exists...
+    // TODO: treat this as a bug?
+    free(new_entry);
+    return probe->value;
+  } else {
+    // new value
+    probe->name = strdup(probe->name); // drop ownership of name
+    probe->value = tt_next++;
+    if ((probe->value - TT_START) >= tt_by_id_sz) {
+      if (tt_by_id_sz == 0)
+	tt_by_id = malloc(sizeof(*tt_by_id) * ((tt_by_id_sz = (tt_next - TT_START) * 16)));
+      else
+	tt_by_id = realloc(tt_by_id, sizeof(*tt_by_id) * ((tt_by_id_sz *= 2)));
+    }
+    assert(probe->value - TT_START < tt_by_id_sz);
+    tt_by_id[probe->value - TT_START] = probe;
+    return probe->value;
+  }
+}
+int h_get_token_type_number(const char* name) {
+  Entry e;
+  e.name = name;
+  Entry **ret = (Entry**)tfind(&e, &tt_registry, compare_entries);
+  if (ret == NULL)
+    return -1;
+  else
+    return (*ret)->value;
+}
+const char* h_get_token_type_name(int token_type) {
+  if (token_type >= tt_next || token_type < TT_START)
+    return NULL;
+  else
+    return tt_by_id[token_type - TT_START]->name;
+}
diff --git a/src/t_misc.c b/src/t_misc.c
index c762c07380bc36db4426c6877d784f329d2ac0bd..74a57ca9b438e75fcbf222b4bbbc79a951c39022 100644
--- a/src/t_misc.c
+++ b/src/t_misc.c
@@ -1,4 +1,5 @@
 #include <glib.h>
+#include <string.h>
 #include "test_suite.h"
 #include "hammer.h"
 
@@ -11,6 +12,24 @@ static void test_tt_user(void) {
   g_check_cmp_int32(TT_USER, >, TT_ERR);
 }
 
+static void test_tt_registry(void) {
+  int id = h_allocate_token_type("com.upstandinghackers.test.token_type");
+  g_check_cmp_int32(id, >=, TT_USER);
+  int id2 = h_allocate_token_type("com.upstandinghackers.test.token_type_2");
+  g_check_cmp_int32(id2, !=, id);
+  g_check_cmp_int32(id2, >=, TT_USER);
+  g_check_cmp_int32(id, ==, h_get_token_type_number("com.upstandinghackers.test.token_type"));
+  g_check_cmp_int32(id2, ==, h_get_token_type_number("com.upstandinghackers.test.token_type_2"));
+  g_check_string("com.upstandinghackers.test.token_type", ==, h_get_token_type_name(id));
+  g_check_string("com.upstandinghackers.test.token_type_2", ==, h_get_token_type_name(id2));
+  if (h_get_token_type_name(0) != NULL) {
+    g_test_message("Unknown token type should not return a name");
+    g_test_fail();
+  }
+  g_check_cmp_int32(h_get_token_type_number("com.upstandinghackers.test.unkown_token_type"), ==, -1);
+}
+
 void register_misc_tests(void) {
   g_test_add_func("/core/misc/tt_user", test_tt_user);
+  g_test_add_func("/core/misc/tt_registry", test_tt_registry);
 }
diff --git a/src/t_parser.c b/src/t_parser.c
index 37c5250f1196e136e0729b9fbc8c068f8663f20f..e2eca978e9e96b341b04d55ba8a850d95dacae54 100644
--- a/src/t_parser.c
+++ b/src/t_parser.c
@@ -162,7 +162,7 @@ static void test_middle(gconstpointer backend) {
 
 #include <ctype.h>
 
-HParsedToken* upcase(const HParseResult *p) {
+HParsedToken* upcase(const HParseResult *p, void* user_data) {
   switch(p->ast->token_type) {
   case TT_SEQUENCE:
     {
@@ -202,7 +202,8 @@ static void test_action(gconstpointer backend) {
 							h_ch('B'), 
 						      NULL), 
 					       NULL), 
-				    upcase);
+				    upcase,
+				    NULL);
   
   g_check_parse_match(action_, (HParserBackend)GPOINTER_TO_INT(backend), "ab", 2, "(u0x41 u0x42)");
   g_check_parse_match(action_, (HParserBackend)GPOINTER_TO_INT(backend), "AB", 2, "(u0x41 u0x42)");
@@ -364,7 +365,7 @@ static void test_epsilon_p(gconstpointer backend) {
   g_check_parse_match(epsilon_p_3, (HParserBackend)GPOINTER_TO_INT(backend), "a", 1, "(u0x61)");
 }
 
-bool validate_test_ab(HParseResult *p) {
+bool validate_test_ab(HParseResult *p, void* user_data) {
   if (TT_SEQUENCE != p->ast->token_type) 
     return false;
   if (TT_UINT != p->ast->seq->elements[0]->token_type)
@@ -376,7 +377,8 @@ bool validate_test_ab(HParseResult *p) {
 
 static void test_attr_bool(gconstpointer backend) {
   const HParser *ab_ = h_attr_bool(h_many1(h_choice(h_ch('a'), h_ch('b'), NULL)),
-				   validate_test_ab);
+				   validate_test_ab,
+				   NULL);
 
   g_check_parse_match(ab_, (HParserBackend)GPOINTER_TO_INT(backend), "aa", 2, "(u0x61 u0x61)");
   g_check_parse_match(ab_, (HParserBackend)GPOINTER_TO_INT(backend), "bb", 2, "(u0x62 u0x62)");
@@ -433,7 +435,7 @@ static void test_ambiguous(gconstpointer backend) {
   HParser *p_ = h_ch('+');
   HParser *E_ = h_indirect();
   h_bind_indirect(E_, h_choice(h_sequence(E_, p_, E_, NULL), d_, NULL));
-  HParser *expr_ = h_action(E_, h_act_flatten);
+  HParser *expr_ = h_action(E_, h_act_flatten, NULL);
 
   g_check_parse_match(expr_, (HParserBackend)GPOINTER_TO_INT(backend), "d", 1, "(u0x64)");
   g_check_parse_match(expr_, (HParserBackend)GPOINTER_TO_INT(backend), "d+d", 3, "(u0x64 u0x2b u0x64)");
diff --git a/tools/scanreplace.py b/tools/scanreplace.py
new file mode 100644
index 0000000000000000000000000000000000000000..5321e4813d9ee0030964c4dd1bcf207710808037
--- /dev/null
+++ b/tools/scanreplace.py
@@ -0,0 +1,15 @@
+from string import Template
+
+def replace_action(target, source, env):
+  open(str(target[0]), 'w').write(Template(open(str(source[0]), 'r').read()).safe_substitute(env))
+  return 0
+
+def replace_string(target, source, env):
+  return "building '%s' from '%s'" % (str(target[0]), str(source[0]))
+
+def generate(env, **kw):
+  action = env.Action(replace_action, replace_string)
+  env['BUILDERS']['ScanReplace'] = env.Builder(action=action, src_suffix='.in', single_source=True)
+
+def exists(env):
+  return 1