Multidimensional array support

README.md

@@ -263,11 +263,14 @@ When writing, the following type mappings are also available:
 | character           | string (`string`)                                                   |
 | pathname            | string (`uiop:native-namestring`)                                   |
 | real                | number                                                              |
+| array               | array\* - multidimensional arrays are arrays-of-arrays              |
 | sequence            | array                                                               |
 | standard-object     | object                                                              |
-| structure-object\*  | object                                                              |
+| structure-object†   | object                                                              |
 
-\*: On supported implementations where structure slots are available via the MOP.
+\*: `#2A((1 2) (3 4))` becomes `[[1,2],[3,4]]`
+
+†: On supported implementations where structure slots are available via the MOP.
 
 If you have an alist/plist you wish to write, we recommend the use of either `alexandria:alist-hash-table` or `alexandria:plist-hash-table`, or use one of the methods in [Custom Serialization](#custom-serialization).
 

src/jzon.lisp

@@ -1408,6 +1408,21 @@ see `write-values'"
   (:method  ((writer writer) (value pathname))
     (%write-json-atom writer (uiop:native-namestring value)))
 
+  ;; Multi-dimensional arrays
+  (:method ((writer writer) (value array))
+    (let ((dimensions (array-dimensions value)))
+      (if (null dimensions)
+          (write-value writer (aref value))
+          (labels ((recurse (dimensions acc)
+                     (destructuring-bind (d . rest) dimensions
+                       (with-array writer
+                         (if (null rest)
+                           (loop :for i :below d
+                                 :do (write-value writer (row-major-aref value (+ acc i))))
+                           (loop :for i :below d
+                                 :do (recurse rest (+ acc (* i d)))))))))
+            (recurse dimensions 0)))))
+
   ;;; Sequence support
   (:method ((writer writer) (value sequence))
     (with-array writer

test/jzon-tests.lisp

@@ -764,6 +764,12 @@
   ]
 ]" (jzon:stringify #(#(1 2) #(3 4)) :pretty t))))
 
+(test stringify-multidimensional-array
+  (is (string= "[[1,2],[3,4]]" (jzon:stringify #2A((1 2) (3 4))))))
+
+(test 0-dimension-array
+  (is (string= "42" (jzon:stringify #0A42))))
+
 (defun recode (value)
   "Shorthand for (jzon:parse (jzon:stringify value))"
   (jzon:parse (jzon:stringify value)))
@@ -855,9 +861,6 @@
   }
 ]" (jzon:stringify (vector (ph "x" 0)) :pretty t))))
 
-(test stringify-no-slots-on-unknown-object ()
-  (is (string= "{}" (jzon:stringify (make-array '(2 2))))))
-
 (test stringify-pretty-prints-keys
   (is (string= "{\"#(1 2)\":0}" (jzon:stringify (ph #(1 2) 0)))))