preserve=?

implementations/racket/preserves/preserves/order.rkt

@@ -2,6 +2,7 @@
 
 (provide preserve-order
          preserve<?
+         preserve=?
          sorted-set-elements
          sorted-dict-entries
          sorted-dict-keys-and-values
@@ -71,6 +72,7 @@
                          [_ (datum-order a b)])]))))
 
 (define preserve<? (order-<? preserve-order))
+(define preserve=? (order-=? preserve-order))
 
 ;;---------------------------------------------------------------------------
 ;; Sorting & cached sorted items