Type union-products.

rs.rkt

@@ -5,7 +5,7 @@
 
   (provide
    Species (struct-out reaction) Reaction ReactionName ReactionSystem
-   make-reaction enabled? list-enabled)
+   make-reaction enabled? list-enabled union-products)
 
   (module+ test
     (require typed/rackunit))
@@ -57,6 +57,26 @@
                        'b (make-reaction '(x y) '() '(z))))
       (check-equal? (list-enabled rs (set 'x 'y)) '(b))
       (check-equal? (list-enabled rs (set 'x)) '(a))))
+
+  (: union-products (-> ReactionSystem (Listof ReactionName) (Setof Species)))
+  (define (union-products rs as)
+    (cond
+      [(empty? as) (set)]
+      [else (define products (for/list : (Listof (Setof Species))
+                                       ([a as])
+                               (reaction-products (hash-ref rs a))))
+            (apply set-union (assert-type products (NonemptyListof (Setof Species))))]))
+
+  (module+ test
+    (test-case "union-products"
+      (define rs (hash 'a (make-reaction '(x) '(y) '(z))
+                       'b (make-reaction '(x y) '() '(t))))
+      (check-equal? (union-products rs '(a b))
+                    (set 't 'z))
+      (check-equal? (union-products rs '(a))
+                    (set 'z))
+      (check-equal? (union-products rs '())
+                    (set))))
   )
 
 (require graph "utils.rkt" "generic.rkt")

scribblings/rs.scrbl

@@ -99,6 +99,18 @@ Returns the list of the names of reactions of @racket[rs] enabled on
           (list-enabled rs (set 'x))))
 ]}
 
+@defproc[(union-products [rs ReactionSystem] [as (Listof ReactionName)])
+			 (Setof Species)]{
+
+Returns the union of the product sets of the given reactions listed in
+@racket[as] in @racket[rs].  If no reactions are supplied, returns the
+empty set.
+
+@ex[
+(union-products (hash 'a (make-reaction '(x) '(y) '(z))
+                      'b (make-reaction '(x y) '() '(z)))
+                '(a b))
+]}
 
 
 @section{Org-mode interaction}