Initial data commit

Task/Stack/Jq/stack-5.jq

@@ -0,0 +1,12 @@
+# Input: an object
+# Output: the updated object with .emit filled in from `update|emit`.
+# `emit` may produce a stream of values, which need not be strings.
+def observe(update; emit):
+  def s(stream): reduce stream as $_ (null;
+    if $_ == null then .
+    elif . == null then "\($_)"
+    else . + "\n\($_)"
+    end);
+  .emit as $x
+  | update
+  | .emit = s($x // null, emit);