Add loop macro and a test

lib/Minilisp.pm

@@ -977,6 +977,25 @@ sub macro_return {
 }
 $macros{'return'} = \&macro_return;
 
+sub macro_loop {
+  my $ts = shift;
+
+  my $inner = macro_progn($ts);
+
+  return create_block(
+    "nil",
+    sub {
+      my $ctx = shift;
+
+      while (1)
+        {
+          $inner->($ctx);
+        }
+    }
+  );
+}
+$macros{loop} = \&macro_loop;
+
 sub compile {
   my ($term) = @_;
   my @tokens = tokenize($term);

t/loop.t

@@ -0,0 +1,6 @@
+(expect "loop"
+        (equal (let ((i 0))
+                 (loop (set i (+ i 1))
+                       (when (> i 3)
+                         (return i))))
+               4))