sets: adding intersect!.

core/sets/sets-docs.factor

@@ -27,6 +27,7 @@ ARTICLE: "set-operations" "Operations on sets"
     clear-set
     union!
     diff!
+    intersect!
 }
 "To test if a set is the empty set:"
 { $subsections null? }
@@ -172,6 +173,11 @@ HELP: diff!
 { $description "Removes all members from " { $snippet "set1" } " contained in " { $snippet "set2" } "." }
 { $side-effects "set1" } ;
 
+HELP: intersect!
+{ $values { "set1" set } { "set2" set } }
+{ $description "Removes all members from " { $snippet "set1" } " not contained in " { $snippet "set2" } "." }
+{ $side-effects "set1" } ;
+
 HELP: intersects?
 { $values { "set1" set } { "set2" set } { "?" "a boolean" } }
 { $description "Tests if " { $snippet "set1" } " and " { $snippet "set2" } " have any elements in common." }

core/sets/sets-tests.factor

@@ -140,3 +140,8 @@ M: null-set members drop f ;
 [ HS{ 1 } ] [ HS{ 1 2 3 } HS{ 2 3 } diff! ] unit-test
 [ HS{ 1 } ] [ HS{ 1 } HS{ 2 3 4 } diff! ] unit-test
 [ HS{ 1 2 3 } ] [ HS{ 1 2 3 } HS{ 4 } diff! ] unit-test
+
+[ HS{ } ] [ HS{ } HS{ } intersect! ] unit-test
+[ HS{ 2 3 } ] [ HS{ 1 2 3 } HS{ 2 3 } intersect! ] unit-test
+[ HS{ } ] [ HS{ 1 } HS{ 2 3 4 } intersect! ] unit-test
+[ HS{ } ] [ HS{ 1 2 3 } HS{ 4 } intersect! ] unit-test

core/sets/sets.factor

@@ -168,6 +168,10 @@ M: sequence clear-set
     dupd sequence/tester [ dup ] prepose pick
     [ delete ] curry [ [ drop ] if ] curry compose each ;
 
+: intersect! ( set1 set2 -- set1 )
+    dupd sequence/tester [ dup ] prepose [ not ] compose pick
+    [ delete ] curry [ [ drop ] if ] curry compose each ;
+
 ! Temporarily for compatibility
 
 : unique ( seq -- assoc )