lua: generic for-in; ipairs/pairs/next; arity-tolerant fns +9 tests

lib/lua/runtime.sx

@@ -448,3 +448,84 @@
         (cond
           ((lua-multi? r) (cons (quote lua-multi) (cons true (rest r))))
           (else (list (quote lua-multi) true r)))))))
+
+(define
+  lua-ipairs-iter
+  (fn
+    (t i)
+    (let
+      ((nk (+ i 1)))
+      (let
+        ((v (get t (str nk))))
+        (if (= v nil) nil (list (quote lua-multi) nk v))))))
+
+(define
+  lua-ipairs
+  (fn
+    (t)
+    (list (quote lua-multi) lua-ipairs-iter t 0)))
+
+(define ipairs lua-ipairs)
+
+(define
+  lua-next-skip-meta
+  (fn
+    (ks)
+    (cond
+      ((= (len ks) 0) (list))
+      ((= (first ks) "__meta") (lua-next-skip-meta (rest ks)))
+      (else ks))))
+
+(define
+  lua-next-after
+  (fn
+    (ks prev-key)
+    (cond
+      ((= (len ks) 0) (list))
+      ((= (first ks) (str prev-key)) (lua-next-skip-meta (rest ks)))
+      (else (lua-next-after (rest ks) prev-key)))))
+
+(define
+  lua-key-to-value
+  (fn
+    (k)
+    (cond
+      ((= k "true") true)
+      ((= k "false") false)
+      (else
+        (let
+          ((n (lua-to-number k))) (if (= n nil) k n))))))
+
+(define
+  lua-next
+  (fn
+    (&rest args)
+    (let
+      ((t (first args))
+        (prev (if (> (len (rest args)) 0) (first (rest args)) nil)))
+      (let
+        ((all-keys (keys t)))
+        (let
+          ((ks (if (= prev nil) (lua-next-skip-meta all-keys) (lua-next-after all-keys prev))))
+          (cond
+            ((= (len ks) 0) nil)
+            (else
+              (let
+                ((k (first ks)))
+                (list (quote lua-multi) (lua-key-to-value k) (get t k))))))))))
+
+(define next lua-next)
+
+(define
+  lua-pairs
+  (fn
+    (t)
+    (list (quote lua-multi) lua-next t nil)))
+
+(define pairs lua-pairs)
+
+(define
+  lua-arg
+  (fn
+    (args i)
+    (if (< i (len args)) (nth args i) nil)))