utils: Type extract-symbols.

scribblings/utils.scrbl

@@ -2,7 +2,7 @@
 @(require scribble/example racket/sandbox
 	  (for-label racket graph (submod "../utils.rkt" typed)
 	  	     (only-in typed/racket/base
-		     	      Any AnyValues)))
+		     	      Any AnyValues Listof Symbol)))
 
 @title[#:tag "utils"]{dds/utils: Various Utilities}
 
@@ -116,6 +116,17 @@ Note that only one expression can be supplied in the body.
 
 @section{Analysis of quoted expressions}
 
+@defproc[(extract-symbols [form Any]) (Listof Symbol)]{
+
+Produces a list of symbols appearing in the quoted expression
+passed in the first argument.
+
+@examples[#:eval utils-evaluator
+(extract-symbols '(1 (2 3) x (y z 3)))
+]
+
+}
+
 @section{Org-mode interoperability}
 
 Org-mode supports laying out the output of code blocks as tables, which is very

utils.rkt

@@ -14,7 +14,8 @@
   (require typed/graph typed/rackunit
            (for-syntax syntax/parse racket/list))
 
-  (provide eval-with eval1-with auto-hash-ref/explicit auto-hash-ref/:)
+  (provide eval-with eval1-with auto-hash-ref/explicit auto-hash-ref/:
+           extract-symbols)
 
   (define-type Variable Symbol)
   (define-type (VariableMapping A) (Immutable-HashTable Variable A))
@@ -100,17 +101,35 @@
       (let ([x-str (symbol->string x)])
         (if (eq? #\: (string-ref x-str 0))
             (string->symbol (substring x-str 1))
-            x)))))
+            x))))
+
+  (: extract-symbols (-> Any (Listof Symbol)))
+  (define (extract-symbols form)
+    (: extract-rec (-> Any (Listof Any)))
+    (define (extract-rec form)
+      (match form
+        [(? symbol?) (list form)]
+        [(? list?)
+         (flatten (for/list : (Listof Any)
+                      ([x form])
+                    (extract-symbols x)))]
+        [else '()]))
+    (cast (extract-rec form) (Listof Symbol)))
+
+  (module+ test
+    (test-case "extract-symbols"
+      (check-equal? (extract-symbols '(1 (2 3) x (y z 3)))
+                    '(x y z)))))
 
 (require 'typed)
-(provide eval-with eval1-with auto-hash-ref/explicit auto-hash-ref/:)
+(provide eval-with eval1-with auto-hash-ref/explicit auto-hash-ref/:
+         extract-symbols)
 
 ;;; Untyped section.
 
 (provide
  ;; Functions
- (contract-out [extract-symbols (-> any/c list?)]
-               [any->string (-> any/c string?)]
+ (contract-out [any->string (-> any/c string?)]
                [stringify-variable-mapping (-> variable-mapping? string-variable-mapping?)]
                [string->any (-> string? any/c)]
                [read-org-sexp (-> string? (listof any/c))]
@@ -160,26 +179,6 @@
 
 (define (variable-mapping? dict) (hash/c symbol? any/c))
 
-
-;;; ==============================
-;;; Analysis of quoted expressions
-;;; ==============================
-
-;;; Produces a list of symbols appearing in the quoted expression
-;;; passed in the first argument.
-(define (extract-symbols form)
-  (match form
-    [(? symbol?) (list form)]
-    [(? list?) (flatten (for/list ([x form])
-                          (extract-symbols x)))]
-    [else '()]))
-
-(module+ test
-  (test-case "extract-symbols"
-    (check-equal? (extract-symbols '(1 (2 3) x (y z 3)))
-                  '(x y z))))
-
-
 ;;; =========================
 ;;; Interaction with Org-mode
 ;;; =========================