Fix test failures

library/collections/sequences.factor

@@ -51,6 +51,7 @@ M: object set-nth-unsafe set-nth ;
 M: f length drop 0 ;
 M: f nth nip ;
 M: f nth-unsafe nip ;
+M: f like drop dup empty? [ drop f ] when ;
 
 ! Integers support the sequence protocol
 M: integer length ;

library/generic/math-combination.factor

@@ -21,12 +21,17 @@ math namespaces sequences words ;
     [ math-class-compare 0 > ] 2keep ? ;
 
 : (math-upgrade) ( max class -- quot )
-    dupd = [ drop [ ] ] [ "coercer" word-prop ] if ;
+    dupd = [
+        drop [ ]
+    ] [
+        "coercer" word-prop [ [ ] ] unless*
+    ] if ;
 
 : math-upgrade ( left right -- quot )
     [ math-class-max ] 2keep
     >r over r> (math-upgrade)
-    >r (math-upgrade) dup [ 1 make-dip ] when r> append ;
+    >r (math-upgrade) dup empty? [ 1 make-dip ] unless
+    r> append ;
 
 TUPLE: no-math-method left right generic ;
 

library/test/collections/sequences.factor

@@ -91,9 +91,9 @@ unit-test
 [ [ 3 2 1 ] ] [ [ 1 2 3 ] reverse ] unit-test
 
 [ f ] [ 0 f head ] unit-test
-[ f ] [ 0 [ 1 ] head ] unit-test
+[ [ ] ] [ 0 [ 1 ] head ] unit-test
 [ [ 1 2 3 ] ] [ 3 [ 1 2 3 4 ] head ] unit-test
-[ f ] [ 3 [ 1 2 3 ] tail ] unit-test
+[ [ ] ] [ 3 [ 1 2 3 ] tail ] unit-test
 [ [ 3 ] ] [ 2 [ 1 2 3 ] tail ] unit-test
 
 [ t ] [ [ 1 2 3 ] [ 1 2 3 ] sequence= ] unit-test

library/test/memory.factor

@@ -1,5 +1,5 @@
 IN: temporary
-USING: generic kernel lists math memory words prettyprint 
+USING: generic kernel math memory words prettyprint 
 sequences test ;
 
 TUPLE: testing x y z ;
@@ -9,14 +9,9 @@ TUPLE: testing x y z ;
 [ ] [
     num-types [
         type>class [
-            dup \ cons = [
-                ! too many conses!
-                drop
-            ] [
-                "predicate" word-prop instances [
-                    class drop
-                ] each
-            ] if
+            "predicate" word-prop instances [
+                class drop
+            ] each
         ] when*
     ] each
 ] unit-test