     [ in>> <and-class> ] bi
     prefix <and-class> ;
 
-: get-transitions ( partition state-transitions -- next-states )
-    [ in>> ] dip '[ _ at ] gather sift ;
+: singleton-partition ( integer non-integers -- {class,partition} )
+    dupd
+    '[ _ [ class-member? ] with filter ] keep
+    prefix f parts boa
+    2array ;
+
+: add-out ( seq partition -- partition' )
+    [ out>> append ] [ in>> ] bi swap parts boa ;
+
+: intersection ( seq -- elts )
+    [ f ] [ unclip [ intersect ] reduce ] if-empty ;
+
+: meaningful-integers ( partition table -- integers )
+    [ [ in>> ] [ out>> ] bi ] dip
+    '[ [ _ at ] map intersection ] bi@ diff ;
+
+: class-integers ( classes integers -- table )
+    '[ _ over '[ _ class-member? ] filter ] H{ } map>assoc ;
+
+: add-integers ( partitions classes integers -- partitions )
+    class-integers '[
+        [ _ meaningful-integers ] keep add-out
+    ] map ;
+
+: class-partitions ( classes -- assoc )
+    [ integer? ] partition [
+        dup powerset-partition spin add-integers
+        [ [ partition>class ] keep 2array ] map
+        [ first ] filter
+    ] [ '[ _ singleton-partition ] map ] 2bi append ;
 
 : new-transitions ( transitions -- assoc ) ! assoc is class, partition
     values [ keys ] gather
     [ tagged-epsilon? not ] filter
-    powerset-partition
-    [ [ partition>class ] keep ] { } map>assoc
-    [ drop ] assoc-filter ;
+    class-partitions ;
+
+: get-transitions ( partition state-transitions -- next-states )
+    [ in>> ] dip '[ _ at ] gather sift ;
 
 : preserving-epsilon ( state-transitions quot -- new-state-transitions )
     [ [ drop tagged-epsilon? ] assoc-filter ] bi
     assoc-union H{ } assoc-like ; inline
+
 : disambiguate ( nfa -- nfa )  
     expand-ors [
         dup new-transitions '[

: make-partition ( choices classes -- partition )
    zip [ first ] partition [ values ] bi@ parts boa ;

: powerset-partition ( classes -- partitions )
    [ length [ 2^ ] keep ] keep '[
        _ <bits> _ make-partition
    ] map rest ;

! Copyright (C) 2009 Daniel Ehrenberg.
! See http://factorcode.org/license.txt for BSD license.
USING: kernel accessors regexp.classes math.bits assocs sequences
arrays sets regexp.dfa math fry regexp.minimize regexp.ast
locals regexp.transition-tables ;
IN: regexp.disambiguate

TUPLE: parts in out ;
