utils: Add pretty-print-set.

utils-tests.rkt

@@ -107,3 +107,6 @@
     (check-false (has-edge? new-gr3 'cc 'bb))
     (check-equal? (edge-weight new-gr3 'aa 'bb) 20)
     (check-equal? (edge-weight new-gr3 'bb 'cc) 22)))
+
+(test-case "Pretty printing"
+  (check-equal? (pretty-print-set (set 'a 'b 1)) "1 a b"))

utils.rkt

@@ -23,7 +23,8 @@
                [update-graph (->* (graph?)
                                   (#:v-func (-> any/c any/c)
                                    #:e-func (-> any/c any/c))
-                                  graph?)])
+                                  graph?)]
+               [pretty-print-set (-> generic-set? string?)])
  ;; Contracts
  (contract-out [variable-mapping? contract?]
                [string-variable-mapping? contract?]
@@ -249,3 +250,12 @@
     (if (unweighted-graph? gr)
         (unweighted-graph/directed edges)
         (weighted-graph/directed edges))))
+
+
+;;; ===============
+;;; Pretty printing
+;;; ===============
+
+;;; Pretty print a set by listing its elements in alphabetic order.
+(define (pretty-print-set s)
+  (string-join (sort (set-map s any->string) string<?)))