diff --git a/Lib/sre_compile.py b/Lib/sre_compile.py
index 9fdc8f3..0829c00 100644
--- a/Lib/sre_compile.py
+++ b/Lib/sre_compile.py
@@ -26,52 +26,12 @@
     # internal: compile a (sub)pattern
     emit = code.append
     for op, av in pattern:
-        if op is ANY:
-            if flags & SRE_FLAG_DOTALL:
-                emit(OPCODES[op])
-            else:
-                emit(OPCODES[CATEGORY])
-                emit(CHCODES[CATEGORY_NOT_LINEBREAK])
-        elif op in (SUCCESS, FAILURE):
-            emit(OPCODES[op])
-        elif op is AT:
-            emit(OPCODES[op])
-            if flags & SRE_FLAG_MULTILINE:
-                emit(ATCODES[AT_MULTILINE[av]])
-            else:
-                emit(ATCODES[av])
-        elif op is BRANCH:
-            emit(OPCODES[op])
-            tail = []
-            for av in av[1]:
-                skip = len(code); emit(0)
-                _compile(code, av, flags)
-                emit(OPCODES[JUMP])
-                tail.append(len(code)); emit(0)
-                code[skip] = len(code) - skip
-            emit(0) # end of branch
-            for tail in tail:
-                code[tail] = len(code) - tail
-        elif op is CALL:
-            emit(OPCODES[op])
-            skip = len(code); emit(0)
-            _compile(code, av, flags)
-            emit(OPCODES[SUCCESS])
-            code[skip] = len(code) - skip
-        elif op is CATEGORY:
-            emit(OPCODES[op])
-            if flags & SRE_FLAG_LOCALE:
-                emit(CHCODES[CH_LOCALE[av]])
-            elif flags & SRE_FLAG_UNICODE:
-                emit(CHCODES[CH_UNICODE[av]])
-            else:
-                emit(CHCODES[av])
-        elif op is GROUP:
+        if op in (LITERAL, NOT_LITERAL):
             if flags & SRE_FLAG_IGNORECASE:
                 emit(OPCODES[OP_IGNORE[op]])
             else:
                 emit(OPCODES[op])
-            emit(av-1)
+            emit(ord(av))
         elif op is IN:
             if flags & SRE_FLAG_IGNORECASE:
                 emit(OPCODES[OP_IGNORE[op]])
@@ -101,15 +61,12 @@
                     raise error, "internal: unsupported set operator"
             emit(OPCODES[FAILURE])
             code[skip] = len(code) - skip
-        elif op in (LITERAL, NOT_LITERAL):
-            if flags & SRE_FLAG_IGNORECASE:
-                emit(OPCODES[OP_IGNORE[op]])
-            else:
+        elif op is ANY:
+            if flags & SRE_FLAG_DOTALL:
                 emit(OPCODES[op])
-            emit(ord(av))
-        elif op is MARK:
-            emit(OPCODES[op])
-            emit(av)
+            else:
+                emit(OPCODES[CATEGORY])
+                emit(CHCODES[CATEGORY_NOT_LINEBREAK])
         elif op in (REPEAT, MIN_REPEAT, MAX_REPEAT):
             if flags & SRE_FLAG_TEMPLATE:
                 emit(OPCODES[REPEAT])
@@ -150,6 +107,49 @@
             if group:
                 emit(OPCODES[MARK])
                 emit((group-1)*2+1)
+        elif op in (SUCCESS, FAILURE):
+            emit(OPCODES[op])
+        elif op in (ASSERT, ASSERT_NOT, CALL):
+            emit(OPCODES[op])
+            skip = len(code); emit(0)
+            _compile(code, av, flags)
+            emit(OPCODES[SUCCESS])
+            code[skip] = len(code) - skip
+        elif op is AT:
+            emit(OPCODES[op])
+            if flags & SRE_FLAG_MULTILINE:
+                emit(ATCODES[AT_MULTILINE[av]])
+            else:
+                emit(ATCODES[av])
+        elif op is BRANCH:
+            emit(OPCODES[op])
+            tail = []
+            for av in av[1]:
+                skip = len(code); emit(0)
+                _compile(code, av, flags)
+                emit(OPCODES[JUMP])
+                tail.append(len(code)); emit(0)
+                code[skip] = len(code) - skip
+            emit(0) # end of branch
+            for tail in tail:
+                code[tail] = len(code) - tail
+        elif op is CATEGORY:
+            emit(OPCODES[op])
+            if flags & SRE_FLAG_LOCALE:
+                emit(CHCODES[CH_LOCALE[av]])
+            elif flags & SRE_FLAG_UNICODE:
+                emit(CHCODES[CH_UNICODE[av]])
+            else:
+                emit(CHCODES[av])
+        elif op is GROUP:
+            if flags & SRE_FLAG_IGNORECASE:
+                emit(OPCODES[OP_IGNORE[op]])
+            else:
+                emit(OPCODES[op])
+            emit(av-1)
+        elif op is MARK:
+            emit(OPCODES[op])
+            emit(av)
         else:
             raise ValueError, ("unsupported operand type", op)
 
diff --git a/Lib/sre_constants.py b/Lib/sre_constants.py
index f5e7894..45f4f48 100644
--- a/Lib/sre_constants.py
+++ b/Lib/sre_constants.py
@@ -23,6 +23,7 @@
 
 ANY = "any"
 ASSERT = "assert"
+ASSERT_NOT = "assert_not"
 AT = "at"
 BRANCH = "branch"
 CALL = "call"
@@ -81,7 +82,7 @@
     FAILURE, SUCCESS,
 
     ANY,
-    ASSERT,
+    ASSERT, ASSERT_NOT,
     AT,
     BRANCH,
     CALL,
@@ -121,8 +122,8 @@
     d = {}
     i = 0
     for item in list:
-	d[item] = i
-	i = i + 1
+        d[item] = i
+        i = i + 1
     return d
 
 OPCODES = makedict(OPCODES)
@@ -176,12 +177,27 @@
 if __name__ == "__main__":
     import string
     def dump(f, d, prefix):
-	items = d.items()
-	items.sort(lambda a, b: cmp(a[1], b[1]))
-	for k, v in items:
-	    f.write("#define %s_%s %s\n" % (prefix, string.upper(k), v))
+        items = d.items()
+        items.sort(lambda a, b: cmp(a[1], b[1]))
+        for k, v in items:
+            f.write("#define %s_%s %s\n" % (prefix, string.upper(k), v))
     f = open("sre_constants.h", "w")
-    f.write("/* generated from sre_constants.py */\n")
+    f.write("""\
+/*
+ * Secret Labs' Regular Expression Engine
+ *
+ * regular expression matching engine
+ *
+ * NOTE: This file is generated by sre_constants.py.  If you need
+ * to change anything in here, edit sre_constants.py and run it.
+ *
+ * Copyright (c) 1997-2000 by Secret Labs AB.  All rights reserved.
+ *
+ * See the _sre.c file for information on usage and redistribution.
+ */
+
+""")
+
     dump(f, OPCODES, "SRE_OP")
     dump(f, ATCODES, "SRE")
     dump(f, CHCODES, "SRE")
diff --git a/Lib/sre_parse.py b/Lib/sre_parse.py
index a6f3082..d3dbe00 100644
--- a/Lib/sre_parse.py
+++ b/Lib/sre_parse.py
@@ -470,6 +470,25 @@
                         if source.next is None or source.next == ")":
                             break
                         source.get()
+                elif source.next in ("=", "!"):
+                    # lookahead assertions
+                    char = source.get()
+                    b = []
+                    while 1:
+                        p = _parse(source, state, flags)
+                        if source.next == ")":
+                            if b:
+                                b.append(p)
+                                p = _branch(state, b)
+                            if char == "=":
+                                subpattern.append((ASSERT, p))
+                            else:
+                                subpattern.append((ASSERT_NOT, p))
+                            break
+                        elif source.match("|"):
+                            b.append(p)
+                        else:
+                            raise error, "pattern not properly closed"
                 else:
                     # flags
                     while FLAGS.has_key(source.next):
diff --git a/Lib/test/output/test_sre b/Lib/test/output/test_sre
index 75caa55..d3732b5 100644
--- a/Lib/test/output/test_sre
+++ b/Lib/test/output/test_sre
@@ -6,7 +6,4 @@
 === grouping error ('([^/]*/)*sub1/', 'd:msgs/tdir/sub1/trial/away.cpp', 0, 'found+"-"+g1', 'd:msgs/tdir/sub1/-tdir/') 'd:msgs/tdir/sub1/-trial/' should be 'd:msgs/tdir/sub1/-tdir/'
 === grouping error ('([abc])*bcd', 'abcd', 0, 'found+"-"+g1', 'abcd-a') 'abcd-c' should be 'abcd-a'
 === grouping error ('(?i)([abc])*bcd', 'ABCD', 0, 'found+"-"+g1', 'ABCD-A') 'ABCD-C' should be 'ABCD-A'
-=== Syntax error: ('a(?!b).', 'abad', 0, 'found', 'ad')
-=== Syntax error: ('a(?=d).', 'abad', 0, 'found', 'ad')
-=== Syntax error: ('a(?=c|d).', 'abad', 0, 'found', 'ad')
 === Failed incorrectly ('^(.+)?B', 'AB', 0, 'g1', 'A')
diff --git a/Modules/_sre.c b/Modules/_sre.c
index 6fcd65e..22b6c73 100644
--- a/Modules/_sre.c
+++ b/Modules/_sre.c
@@ -20,6 +20,7 @@
  * 00-06-28 fl	fixed findall (0.9.1)
  * 00-06-29 fl	fixed split, added more scanner features (0.9.2)
  * 00-06-30 fl	tuning, fast search (0.9.3)
+ * 00-06-30 fl	added assert (lookahead) primitives (0.9.4)
  *
  * Copyright (c) 1997-2000 by Secret Labs AB.  All rights reserved.
  *
@@ -30,7 +31,7 @@
 
 #ifndef SRE_RECURSIVE
 
-char copyright[] = " SRE 0.9.3 Copyright (c) 1997-2000 by Secret Labs AB ";
+char copyright[] = " SRE 0.9.4 Copyright (c) 1997-2000 by Secret Labs AB ";
 
 #include "Python.h"
 
@@ -576,11 +577,10 @@
 			pattern += pattern[0];
 			break;
 
-#if 0
-		case SRE_OP_CALL:
-			/* match subpattern, without backtracking */
+		case SRE_OP_ASSERT:
+			/* assert subpattern */
 			/* args: <skip> <pattern> */
-			TRACE(("%8d: subpattern\n", PTR(ptr)));
+			TRACE(("%8d: assert subpattern\n", PTR(ptr)));
 			state->ptr = ptr;
 			i = SRE_MATCH(state, pattern + 1);
             if (i < 0)
@@ -588,9 +588,20 @@
             if (!i)
 				goto failure;
 			pattern += pattern[0];
-			ptr = state->ptr;
 			break;
-#endif
+
+		case SRE_OP_ASSERT_NOT:
+			/* assert not subpattern */
+			/* args: <skip> <pattern> */
+			TRACE(("%8d: assert not subpattern\n", PTR(ptr)));
+			state->ptr = ptr;
+			i = SRE_MATCH(state, pattern + 1);
+            if (i < 0)
+                return i;
+            if (i)
+				goto failure;
+			pattern += pattern[0];
+			break;
 
 #if 0
 		case SRE_OP_MAX_REPEAT_ONE:
diff --git a/Modules/sre_constants.h b/Modules/sre_constants.h
index 01c8448..2ec00ba 100644
--- a/Modules/sre_constants.h
+++ b/Modules/sre_constants.h
@@ -1,29 +1,42 @@
-/* generated from sre_constants.py */
+/*
+ * Secret Labs' Regular Expression Engine
+ *
+ * regular expression matching engine
+ *
+ * NOTE: This file is generated by sre_constants.py.  If you need
+ * to change anything in here, edit sre_constants.py and run it.
+ *
+ * Copyright (c) 1997-2000 by Secret Labs AB.  All rights reserved.
+ *
+ * See the _sre.c file for information on usage and redistribution.
+ */
+
 #define SRE_OP_FAILURE 0
 #define SRE_OP_SUCCESS 1
 #define SRE_OP_ANY 2
 #define SRE_OP_ASSERT 3
-#define SRE_OP_AT 4
-#define SRE_OP_BRANCH 5
-#define SRE_OP_CALL 6
-#define SRE_OP_CATEGORY 7
-#define SRE_OP_GROUP 8
-#define SRE_OP_GROUP_IGNORE 9
-#define SRE_OP_IN 10
-#define SRE_OP_IN_IGNORE 11
-#define SRE_OP_INFO 12
-#define SRE_OP_JUMP 13
-#define SRE_OP_LITERAL 14
-#define SRE_OP_LITERAL_IGNORE 15
-#define SRE_OP_MARK 16
-#define SRE_OP_MAX_REPEAT 17
-#define SRE_OP_MAX_REPEAT_ONE 18
-#define SRE_OP_MIN_REPEAT 19
-#define SRE_OP_NOT_LITERAL 20
-#define SRE_OP_NOT_LITERAL_IGNORE 21
-#define SRE_OP_NEGATE 22
-#define SRE_OP_RANGE 23
-#define SRE_OP_REPEAT 24
+#define SRE_OP_ASSERT_NOT 4
+#define SRE_OP_AT 5
+#define SRE_OP_BRANCH 6
+#define SRE_OP_CALL 7
+#define SRE_OP_CATEGORY 8
+#define SRE_OP_GROUP 9
+#define SRE_OP_GROUP_IGNORE 10
+#define SRE_OP_IN 11
+#define SRE_OP_IN_IGNORE 12
+#define SRE_OP_INFO 13
+#define SRE_OP_JUMP 14
+#define SRE_OP_LITERAL 15
+#define SRE_OP_LITERAL_IGNORE 16
+#define SRE_OP_MARK 17
+#define SRE_OP_MAX_REPEAT 18
+#define SRE_OP_MAX_REPEAT_ONE 19
+#define SRE_OP_MIN_REPEAT 20
+#define SRE_OP_NOT_LITERAL 21
+#define SRE_OP_NOT_LITERAL_IGNORE 22
+#define SRE_OP_NEGATE 23
+#define SRE_OP_RANGE 24
+#define SRE_OP_REPEAT 25
 #define SRE_AT_BEGINNING 0
 #define SRE_AT_BEGINNING_LINE 1
 #define SRE_AT_BOUNDARY 2