marginally faster nappend

TODO.FACTOR.txt

@@ -65,7 +65,6 @@
 - intrinsic char-slot set-char-slot integer-slot set-integer-slot
 - [ [ dup call ] dup call ] infer hangs
 - declarations
-- optimize away arithmetic dispatch
 - the invalid recursion form case needs to be fixed, for inlines too
 - #jump-f #jump-f-label
 - re-introduce #target-label => #target optimization
@@ -75,8 +74,6 @@
 + sequences
 
 - array sort
-- nappend: instead of using push, enlarge the sequence with set-length
-  then add set the elements with set-nth
 - specialized arrays
 
 + kernel:

library/collections/sequences-epilogue.factor

@@ -112,9 +112,13 @@ M: object >list ( seq -- list ) dup length 0 rot (>list) ;
 : remove  ( obj list -- list ) [ = not ] subset-with ;
 : remq    ( obj list -- list ) [ eq? not ] subset-with ;
 
-: nappend ( s1 s2 -- )
-    #! Destructively append s2 to s1.
-    [ over push ] each drop ;
+: copy-into ( start to from -- )
+    dup length [ >r pick r> + pick set-nth ] 2each 2drop ;
+
+: nappend ( to from -- )
+    >r dup length swap r>
+    over length over length + pick set-length
+    copy-into ;
 
 : append ( s1 s2 -- s1+s2 )
     #! Outputs a new sequence of the same type as s1.
@@ -223,9 +227,6 @@ M: object reverse ( seq -- seq ) [ <reversed> ] keep like ;
         dup pick index dup -1 = [ drop ] [ nip pick nth ] ifte
     ] map 2nip ;
 
-: copy-into ( to from -- )
-    dup length [ pick set-nth ] 2each drop ;
-
 IN: kernel
 
 : depth ( -- n )

library/generic/tuple.factor

@@ -148,9 +148,9 @@ M: mirror set-nth ( n mirror -- elt )
 M: mirror length ( mirror -- len )
     mirror-tuple array-capacity ;
 
-: literal-tuple ( list -- tuple )
+: literal-tuple ( seq -- tuple )
     dup first "tuple-size" word-prop <tuple>
-    [ <mirror> swap copy-into ] keep ;
+    [ <mirror> 0 swap rot copy-into ] keep ;
 
 : clone-tuple ( tuple -- tuple )
     #! Make a shallow copy of a tuple, without cloning its