sequences.modified: simplify M\ summed modified-nth.

extra/sequences/modified/modified.factor

@@ -1,29 +1,33 @@
 ! Copyright (C) 2008 Alex Chapman
 ! See http://factorcode.org/license.txt for BSD license.
-USING: accessors arrays kernel locals math math.order
-sequences sequences.private shuffle ;
+USING: accessors arrays kernel locals math sequences
+sequences.private ;
 IN: sequences.modified
 
 TUPLE: modified ;
 
 GENERIC: modified-nth ( n seq -- elt )
+
 M: modified nth modified-nth ;
 M: modified nth-unsafe modified-nth ;
 
 GENERIC: modified-set-nth ( elt n seq -- )
+
 M: modified set-nth modified-set-nth ;
 M: modified set-nth-unsafe modified-set-nth ;
 
-INSTANCE: modified virtual-sequence
+INSTANCE: modified sequence
 
 TUPLE: 1modified < modified seq ;
 
 M: modified length seq>> length ;
 M: modified set-length seq>> set-length ;
 
-M: 1modified virtual-exemplar seq>> ;
+M: 1modified like seq>> like ;
+M: 1modified new-sequence seq>> new-sequence ;
 
 TUPLE: scaled < 1modified c ;
+
 C: <scaled> scaled
 
 : scale ( seq c -- new-seq )
@@ -37,6 +41,7 @@ M:: scaled modified-set-nth ( elt n seq -- )
     elt seq c>> / n seq seq>> set-nth ;
 
 TUPLE: offset < 1modified n ;
+
 C: <offset> offset
 
 : seq-offset ( seq n -- new-seq )
@@ -49,22 +54,13 @@ M:: offset modified-set-nth ( elt n seq -- )
     elt seq n>> - n seq seq>> set-nth ;
 
 TUPLE: summed < modified seqs ;
+
 C: <summed> summed
 
 M: summed length seqs>> longest length ;
 
-<PRIVATE
-: ?+ ( x/f y/f -- sum )
-    ! addition that treats f as 0
-    [
-        swap [ + ] when*
-    ] [
-        [ ] [ 0 ] if*
-    ] if* ;
-PRIVATE>
-
 M: summed modified-nth ( n seq -- elt )
-    seqs>> [ ?nth ?+ ] with 0 swap reduce ;
+    seqs>> [ ?nth [ + ] when* ] with 0 swap reduce ;
 
 M: summed modified-set-nth ( elt n seq -- ) immutable ;
 
@@ -75,4 +71,5 @@ M: summed virtual-exemplar ( summed -- seq )
     seqs>> ?first ;
 
 : <2summed> ( seq seq -- summed-seq ) 2array <summed> ;
+
 : <3summed> ( seq seq seq -- summed-seq ) 3array <summed> ;