added stx-map to syntax/stx from unstable/syntax

collects/syntax/scribblings/stx.scrbl

@@ -37,6 +37,13 @@ Takes the car of a @techlink[#:doc refman]{syntax pair}.}
 
 Takes the cdr of a @techlink[#:doc refman]{syntax pair}.}
 
+@defproc[(stx-map [proc procedure?]
+                  [stxl stx-list?] ...)
+         list?]{
+
+Equivalent to @racket[(map proc (stx->list stxl) ...)].
+}
+
 @defproc[(module-or-top-identifier=? [a-id identifier?]
 				     [b-id identifier?])
 	 boolean?]{

collects/syntax/stx.rkt

@@ -7,6 +7,7 @@
 
 (provide stx-null? stx-pair? stx-list?
          stx-car stx-cdr stx->list
+         stx-map
          module-or-top-identifier=?)
 
 ;; a syntax null?
@@ -70,6 +71,13 @@
                           #f))))
             e))))
 
+(define (stx-map f . stxls)
+  (for ([stxl (in-list stxls)]
+        [i (in-naturals)])
+    (unless (stx-list? stxl)
+      (apply raise-type-error 'stx-map "stx-list" i stxls)))
+  (apply map f (map stx->list stxls)))
+
 (define (module-or-top-identifier=? a b)
   (or (free-identifier=? a b)
       (and (eq? (syntax-e a) (syntax-e b))