From 7354911d0522649d3418e84e8d249c9a635dc045 Mon Sep 17 00:00:00 2001
From: Simon Forman <sforman@hushmail.com>
Date: Sat, 20 Jul 2019 17:19:35 -0700
Subject: [PATCH] WTF error handler.

Made it check that the unknown term really isn't a literal, definition, function, or combinator.
---
 thun/thun.pl | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/thun/thun.pl b/thun/thun.pl
index 985c877..0e8d2d6 100644
--- a/thun/thun.pl
+++ b/thun/thun.pl
@@ -88,7 +88,15 @@ thun( [Func|E], Si, So) :- func(Func, Si, S), thun(E, S, So).
 thun([Combo|E], Si, So) :- combo(Combo, Si, S, E, Eo), thun(Eo, S, So).
 
 % Some error handling.
-% thun([Unknown|E], Si, So) :- write("wtf? "), writeln(Unknown), So = [[Unknown|E]|Si].
+
+thun([Unknown|E], Si, So) :- damned_thing(Unknown), write("wtf? "), writeln(Unknown), So = [[Unknown|E]|Si].
+
+damned_thing(It) :-
+    \+ literal(It),
+    \+ (It ≡ _),
+    \+ func(It, _, _),
+    \+ combo(It, _, _, _, _).
+
 
 /*
 Literals