Add <flipped> word

basis/columns/columns-docs.factor

@@ -4,7 +4,9 @@ IN: columns
 ARTICLE: "columns" "Column sequences"
 "A " { $emphasis "column" } " presents a column of a matrix represented as a sequence of rows:"
 { $subsection column }
-{ $subsection <column> } ;
+{ $subsection <column> }
+"A utility word:"
+{ $subsection flipped } ;
 
 HELP: column
 { $class-description "A virtual sequence which presents a fixed column of a matrix represented as a sequence of rows. New instances can be created by calling " { $link <column> } "." } ;
@@ -23,4 +25,9 @@ HELP: <column> ( seq n -- column )
     "In the same sense that " { $link <reversed> } " is a virtual variant of " { $link reverse } ", " { $link <column> } " is a virtual variant of " { $snippet "swap [ nth ] curry map" } "."
 } ;
 
+HELP: <flipped>
+{ $values { "seq" sequence } { "seq'" sequence } }
+{ $description "Outputs a new virtual sequence which presents the transpose of " { $snippet "seq" } "." }
+{ $notes "This is the virtual sequence equivalent of " { $link flip } "." } ;
+
 ABOUT: "columns"

basis/columns/columns.factor

@@ -13,3 +13,6 @@ M: column virtual@ dup col>> -rot seq>> nth bounds-check ;
 M: column length seq>> length ;
 
 INSTANCE: column virtual-sequence
+
+: <flipped> ( seq -- seq' )
+    dup first length [ <column> ] with map ;