Add calculation of close-tangibles

luprex/core/cpp/util.hpp

@@ -9,6 +9,7 @@
 #include <tuple>
 #include <utility>
 #include "luastack.hpp"
+#include "spookyv2.hpp"
 
 namespace util {
 
@@ -29,6 +30,9 @@ std::string id_vector_debug_string(const IdVector &idv);
 // Unions and sorts two ID vectors.
 IdVector sort_union_id_vectors(const IdVector &v1, const IdVector &v2);
 
+// Get a 64-bit hashvalue for an ID vector.
+HashValue hash_id_vector(const IdVector &idv);
+
 // Split a string into multiple strings
 StringVec split(const std::string &s, char sep);