utils: Add any->string.

utils-tests.rkt

@@ -33,3 +33,8 @@
 (test-case "Analysis of quoted expressions"
   (check-equal? (extract-symbols '(1 (2 3) x (y z 3)))
                 '(x y z)))
+
+(test-case "Variable mapping and Org-mode"
+  (check-equal? (any->string 'a) "a")
+  (check-equal? (any->string '(a 1 (x y))) "(a 1 (x y))")
+  (check-equal? (any->string "hello") "hello"))

utils.rkt

@@ -14,7 +14,8 @@
                [variable-mapping? (-> any/c boolean?)]
                [hash-pred (->* (hash?)
                                (#:key-pred any/c #:val-pred any/c)
-                               boolean?)])
+                               boolean?)]
+               [any->string (-> any/c string?)])
  ;; Syntax
  auto-hash-ref/explicit auto-hash-ref/:)
 
@@ -145,3 +146,19 @@
     [(list? form)
      (flatten (for/list ([x form]) (extract-symbols x)))]
     [else '()]))
+
+
+;;; =============================
+;;; Variable mapping and Org-mode
+;;; =============================
+
+;;; Org-mode supports laying out the output of code blocks as tables,
+;;; which is very practical for various variable mappings (e.g.,
+;;; states).  However, when the hash table maps variables to lists,
+;;; Org-mode will create a column per list element, which may or may
+;;; not be the desired effect.  In this section I define some
+;;; utilities for handling such situations.
+
+;;; Converts any value to string.
+(define (any->string x)
+  (with-output-to-string (λ () (display x))))