Allow 'for' and 'cond' to take a multi-expression body (closes #868)

docs/language/api.rst

@@ -267,11 +267,10 @@ is only called on every other value in the list.
     ;; collection is a list of numerical values
 
     (for [x collection]
-      (do
       (side-effect1 x)
       (if (% x 2)
         (continue))
-        (side-effect2 x)))
+      (side-effect2 x))
 
 
 dict-comp

hy/core/macros.hy

@@ -73,10 +73,11 @@
     "check `cond` branch for validity, return the corresponding `if` expr"
     (if (not (= (type branch) HyList))
       (macro-error branch "cond branches need to be a list"))
-    (if (!= (len branch) 2)
-      (macro-error branch "cond branches need two items: a test and a code branch"))
-    (setv (, test thebranch) branch)
-    `(if ~test ~thebranch))
+    (if (< (len branch) 2)
+      (macro-error branch "cond branches need at least two items: a test and one or more code branches"))
+    (setv test (car branch))
+    (setv thebranch (cdr branch))
+    `(if ~test (do ~@thebranch)))
 
   (setv root (check-branch branch))
   (setv latest-branch root)
@@ -102,7 +103,7 @@
    [(empty? body)
     (macro-error None "`for' requires a body to evaluate")]
    [(empty? args) `(do ~@body)]
-   [(= (len args) 2)  `(for* [~@args] ~@body)]
+   [(= (len args) 2)  `(for* [~@args] (do ~@body))]
    [true
     (let [[alist (cut args 0 nil 2)]]
       `(for* [(, ~@alist) (genexpr (, ~@alist) [~@args])] ~@body))]))

tests/native_tests/contrib/walk.hy

@@ -32,4 +32,4 @@
 
 (defn test-macroexpand-all []
   (assert (= (macroexpand-all '(with [a b c] (for [d c] foo)))
-             '(with* [a] (with* [b] (with* [c] (do (for* [d c] foo))))))))
+             '(with* [a] (with* [b] (with* [c] (do (for* [d c] (do foo)))))))))

tests/native_tests/language.hy

@@ -86,10 +86,12 @@
 
 (defn test-for-loop []
   "NATIVE: test for loops"
-  (setv count 0)
+  (setv count1 0 count2 0)
   (for [x [1 2 3 4 5]]
-    (setv count (+ count x)))
-  (assert (= count 15))
+    (setv count1 (+ count1 x))
+    (setv count2 (+ count2 x)))
+  (assert (= count1 15))
+  (assert (= count2 15))
   (setv count 0)
   (for [x [1 2 3 4 5]
         y [1 2 3 4 5]]
@@ -224,7 +226,7 @@
   "NATIVE: test if cond sorta works."
   (cond
    [(= 1 2) (assert (is true false))]
-   [(is null null) (assert (is true true))]))
+   [(is null null) (setv x true) (assert x)]))
 
 
 (defn test-index []