load_thy/after_load: explicit check of parent theories, which might have failed to join proofs -- avoid uninformative crash via Graph.UNDEF;
(* Title: HOL/Library/Code_Prolog.thy
Author: Lukas Bulwahn, TUM 2010
*)
header {* Code generation of prolog programs *}
theory Code_Prolog
imports Main
uses "~~/src/HOL/Tools/Predicate_Compile/code_prolog.ML"
begin
end