Fixing insufficient safety in flip and M: column virtual@

core/sequences/sequences.factor

@@ -221,7 +221,8 @@ TUPLE: column seq col ;
 C: <column> column
 
 M: column virtual-seq column-seq ;
-M: column virtual@ dup column-col -rot column-seq nth ;
+M: column virtual@
+    dup column-col -rot column-seq nth bounds-check ;
 M: column length column-seq length ;
 
 INSTANCE: column virtual-sequence
@@ -546,11 +547,6 @@ M: sequence <=>
 
 : all-eq? ( seq -- ? ) [ eq? ] monotonic? ;
 
-: flip ( matrix -- newmatrix )
-    dup empty? [
-        dup first length [ <column> dup like ] curry* map
-    ] unless ;
-
 : exchange ( m n seq -- )
     pick over bounds-check 2drop 2dup bounds-check 2drop
     exchange-unsafe ;
@@ -667,6 +663,12 @@ PRIVATE>
 : infimum ( seq -- n ) dup first [ min ] reduce ;
 : supremum ( seq -- n ) dup first [ max ] reduce ;
 
+: flip ( matrix -- newmatrix )
+    dup empty? [
+        dup [ length ] map infimum
+        [ <column> dup like ] curry* map
+    ] unless ;
+
 : sequence-hashcode ( n seq -- x )
     0 -rot [
         hashcode* >fixnum swap 31 fixnum*fast fixnum+fast