1 files changed, 2 insertions, 0 deletions
diff --git a/bnf.h b/bnf.h
index 959e1f8..56aacb0 100644
--- a/bnf.h
+++ b/bnf.h
@@ -12,3 +12,5 @@ using namespace std::string_literals;
 using BNF = std::map<std::string, std::vector<std::vector<std::string>>>;
 
 std::map<std::string, std::set<std::string>> Reverse(BNF bnf);
+
+BNF SubBNF(const BNF& bnf, const std::string& top);