1 files changed, 13 insertions, 4 deletions
diff --git a/fib.kpl b/fib.kpl
index f049ba0..cb6b5ef 100644
--- a/fib.kpl
+++ b/fib.kpl
@@ -5,15 +5,24 @@
 */
 
 `export fib : Fn[n] $ (
+    t : `type n
+    ? {
+        t = Int[Any; .signed; Any] {
+            ? n <= 0 { `return 0 }
+        }
+        t = Int[Any; .unsigned; Any] {
+            ? n = 0 { `return 0 }
+        }
+        { `panic "n must be a signed or unsigned Int" }
+    }
     ? {
-        n <= 0 { 0 }
         n < 3 { 2 }
-        { `call_sync(fib; n - 1) + fib `call_sync n - 2 }
+        { `sync(fib; n - 1) + fib `sync n - 2 }
     }
 )
 
 `export fib_string Fn[n] $ (
-    String $ ("fib("; n; ") = "; fib `call_sync n; "\n")
+    String $ ("fib("; n; ") = "; fib `sync n; "\n")
 )
 
 `is_main Fn $ (
@@ -24,5 +33,5 @@
             "Usage: "; args `get 0; " "; args `get 1; " <number>\n"
          )
     }
-    `print fib_string `call_sync I64 $ args `get -1
+    `print fib_string `sync I64 $ args `get -1
 )