diff --git a/extra/sequences/lib/lib-tests.factor b/extra/sequences/lib/lib-tests.factor
index e457139bcd..470cd096e1 100644
--- a/extra/sequences/lib/lib-tests.factor
+++ b/extra/sequences/lib/lib-tests.factor
@@ -1,4 +1,5 @@
-USING: kernel sequences.lib math math.functions tools.test ;
+USING: arrays kernel sequences sequences.lib math
+math.functions tools.test ;
 
 [ 4 ] [ { 1 2 } [ sq ] [ * ] map-reduce ] unit-test
 [ 36 ] [ { 2 3 } [ sq ] [ * ] map-reduce ] unit-test
@@ -28,3 +29,7 @@ USING: kernel sequences.lib math math.functions tools.test ;
 [ -11 -9 ] [ { -11 -10 -9 } minmax ] unit-test
 [ -1/0. 1/0. ] [ { -1/0. 1/0. -11 -10 -9 } minmax ] unit-test
 
+[ { { 1 } { -1 5 } { 2 4 } } ]
+[ { 1 -1 5 2 4 } [ < ] monotonic-split [ >array ] map ] unit-test
+[ { { 1 1 1 1 } { 2 2 } { 3 } { 4 } { 5 } { 6 6 6 } } ]
+[ { 1 1 1 1 2 2 3 4 5 6 6 6 } [ = ] monotonic-split [ >array ] map ] unit-test
diff --git a/extra/sequences/lib/lib.factor b/extra/sequences/lib/lib.factor
index 147af87cc2..d6cf1fe1dc 100644
--- a/extra/sequences/lib/lib.factor
+++ b/extra/sequences/lib/lib.factor
@@ -1,4 +1,4 @@
-USING: combinators.lib kernel sequences math
+USING: combinators.lib kernel sequences math namespaces
 sequences.private shuffle ;
 
 IN: sequences.lib
@@ -46,3 +46,18 @@ IN: sequences.lib
     #! find the min and max of a seq in one pass
     1/0. -1/0. rot [ tuck max >r min r> ] each ;
 
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: ,, building get peek push ;
+: v, V{ } clone , ;
+: ,v building get dup peek empty? [ dup pop* ] when drop ;
+
+: monotonic-split ( seq quot -- newseq )
+    [
+        >r dup unclip add r>
+        v, [ pick ,, call [ v, ] unless ] curry 2each ,v
+    ] { } make ;
+
+: singleton? ( seq -- ? )
+    length 1 = ;
+