add comments on what we should be doing

src/main.zig

@@ -321,6 +321,23 @@ fn processCommand(allocator: std.mem.Allocator, sentence: [:0]const u8, parser:
         };
         defer tree.deinit();
 
+        // Bracketed words are "null"
+        // words with [?] are "unknown"
+        // If we have unknowns, I think we want to replace (or if no replacement
+        // is available, strip) them. Then re-parse immediately, because we're
+        // in a bad enough state that we might screw something else up
+        //
+        // If there are nulls, then we should walk those nulls and look for
+        // replacement values. If any replacements have been performed, then
+        // try re-parsing at that point.
+        //
+        // This might all be best done in the library itself. Pass in the
+        // map of replacement words and let it churn.
+        //
+        // For null words, I think we can use this replacement loop
+        // if (tree.hasUnknowns()) // then what?
+        // {}
+
         const action_words = tree.sentenceAction() catch |err| {
             if (!builtin.is_test)
                 std.log.err("Failed to extract action: {}\nParse tree: {f}", .{ err, tree });

src/root.zig

@@ -151,8 +151,9 @@ pub const ParseTree = struct {
         node = node.child.?;
 
         // We need the next node, which should be our PP node
-        if (node.next == null) @panic("VP node must have a child with two members");
-        node = node.next.?;
+        if (node.next == null) @panic("VP node must have a child with at least two members");
+        while (node.next != null) // fast forward to the very last node at this level
+            node = node.next.?;
 
         // https://opencog.github.io/link-grammar-website/dict/section-PP.html
         if (!std.mem.startsWith(u8, node.label, "PP"))