add for/set

collects/racket/set.rkt

@@ -7,7 +7,9 @@
          set-member? set-add set-remove
          set-union set-intersect set-subtract
          set-map set-for-each 
-         (rename-out [*in-set in-set]))
+         (rename-out [*in-set in-set])
+         for/set for/seteq for/seteqv
+         for*/set for*/seteq for*/seteqv)
 
 (define-struct set (ht)
   #:omit-define-syntaxes
@@ -206,3 +208,17 @@
            #t
            ;; loop args
            ((hash-iterate-next ht pos)))]])))
+
+(define-syntax-rule (define-for for/fold/derived for/set set)
+  (define-syntax (for/set stx)
+    (syntax-case stx ()
+      [(_ bindings . body)
+       (quasisyntax/loc stx
+         (for/fold/derived #,stx ([s (set)]) bindings (set-add s (let () . body))))])))
+
+(define-for for/fold/derived for/set set)
+(define-for for*/fold/derived for*/set set)
+(define-for for/fold/derived for/seteq seteq)
+(define-for for*/fold/derived for*/seteq seteq)
+(define-for for/fold/derived for/seteqv seteqv)
+(define-for for*/fold/derived for*/seteqv seteqv)

collects/scribblings/reference/sets.scrbl

@@ -109,6 +109,7 @@ Applies the procedure @scheme[proc] to each element in
 @scheme[set] in an unspecified order, accumulating the results
 into a list.}
 
+
 @defproc[(set-for-each [set set?]
                        [proc (any/c . -> . any)])
          void?]{
@@ -116,7 +117,21 @@ into a list.}
 Applies @scheme[proc] to each element in @scheme[set] (for the
 side-effects of @scheme[proc]) in an unspecified order.}
 
+
 @defproc[(in-set [set set?]) sequence?]{
 
 Explicitly converts a set to a sequence for use with @scheme[for] and
 other forms.}
+
+@deftogether[(
+@defform[(for/set (for-clause ...) body ...+)]
+@defform[(for/seteq (for-clause ...) body ...+)]
+@defform[(for/seteqv (for-clause ...) body ...+)]
+@defform[(for*/set (for-clause ...) body ...+)]
+@defform[(for*/seteq (for-clause ...) body ...+)]
+@defform[(for*/seteqv (for-clause ...) body ...+)]
+)]{
+
+Analogous to @scheme[for/list] and @scheme[for*/list], but to
+construct a set instead of a list.}
+

collects/tests/mzscheme/set.ss

@@ -102,4 +102,8 @@
 
 ;; ----------------------------------------
 
+(test (set 1 2 3) 'for/set (for/set ([i '(0 1 2)]) (add1 i)))
+
+;; ----------------------------------------
+
 (report-errs)