allow `reverse` on non-lengthable

src/boot/boot.janet

@@ -1435,7 +1435,7 @@
 
 (defn every?
   ``Evaluates to the last element of `ind` if all preceding elements are truthy,
-  otherwise evaluates to the first falsey argument.``
+  otherwise evaluates to the first falsey element.``
   [ind]
   (var res true)
   (loop [x :in ind :while res]
@@ -1455,28 +1455,29 @@
   `Reverses the order of the elements in a given array or buffer and returns it
   mutated.`
   [t]
-  (def len-1 (- (length t) 1))
-  (def half (/ len-1 2))
-  (forv i 0 half
-    (def j (- len-1 i))
-    (def l (in t i))
-    (def r (in t j))
-    (put t i r)
-    (put t j l))
+  (var i 0)
+  (var j (length t))
+  (while (< i (-- j))
+    (def ti (in t i))
+    (put t i (in t j))
+    (put t j ti)
+    (++ i))
   t)
 
 (defn reverse
   `Reverses the order of the elements in a given array or tuple and returns
-  a new array. If a string or buffer is provided, returns an array of its
-  byte values, reversed.`
+  a new array. If a string or buffer is provided, returns a buffer instead.`
   [t]
-  (var n (length t))
-  (def ret (if (bytes? t)
-             (buffer/new-filled n)
-             (array/new-filled n)))
-  (each v t
-    (put ret (-- n) v))
-  ret)
+  (if (lengthable? t)
+    (do
+      (var n (length t))
+      (def ret (if (bytes? t)
+                (buffer/new-filled n)
+                (array/new-filled n)))
+      (each v t
+        (put ret (-- n) v))
+      ret)
+    (reverse! (seq [v :in t] v))))
 
 (defn invert
   ``Given an associative data structure `ds`, returns a new table where the