Add a loop macro.

1 files changed, 11 insertions, 12 deletions

diff --git a/csc/list.csc b/csc/list.csc
index f425146..dcc1766 100644
--- a/csc/list.csc
+++ b/csc/list.csc
@@ -7,27 +7,26 @@
     split-at
     take)
   (import (scheme base)
+          (only (csc loop)
+            loop
+            return)
           (only (csc match)
             match))
   (begin
 
 
     (define (take n xs)
-      (let loop ((n n)
-                 (xs xs)
-                 (acc '()))
-        (if (or (not (positive? n)) (null? xs))
-            (reverse acc)
-          (loop (- n 1) (cdr xs) (cons (car xs) acc)))))
+      (loop for x in xs
+            for i from 1 to n
+            collect x))
 
 
     (define (split-at n xs)
-      (let loop ((n n)
-                 (xs xs)
-                 (acc '()))
-        (if (or (not (positive? n)) (null? xs))
-            (values (reverse acc) xs)
-          (loop (- n 1) (cdr xs) (cons (car xs) acc)))))
+      (loop for i from 1 to n
+            for x in xs
+            collect x into first-half
+            for second-half = xs then (cdr second-half)
+            finally (return (values first-half second-half))))
 
 
     (define (revappend a b)