Data commit

Task/Stack/Babel/stack.pb

@@ -0,0 +1,17 @@
+main :
+    { (1 2 3) foo set     -- foo = (1 2 3)
+    4 foo push            -- foo = (1 2 3 4)
+    0 foo unshift         -- foo = (0 1 2 3 4)
+    foo pop               -- foo = (0 1 2 3)
+    foo shift             -- foo = (1 2 3)
+    check_foo
+    { foo pop } 4 times   -- Pops too many times, but this is OK and Babel won't complain
+    check_foo }
+
+empty? : nil?   -- just aliases 'empty?' to the built-in operator 'nil?'
+
+check_foo! :
+    { "foo is "
+    {foo empty?) {nil} {"not " .} ifte
+    "empty" .
+    cr << }