diff --git a/src/analyse/backtrack.cc b/src/analyse/backtrack.cc
index 5b6c133..3008add 100644
--- a/src/analyse/backtrack.cc
+++ b/src/analyse/backtrack.cc
@@ -7,66 +7,33 @@
 
 // TODO: using const RawCode& instead of uint64_t
 
-struct backtrack_hash {
-//    template <class T1, class T2>
-//    std::size_t operator()(const std::pair<T1, T2> &v) const {
-//        return std::hash<T1>()(v.size());
-//    }
-
-    std::size_t operator()(const Analyse::backtrack_t &b) const {
-        std::cout << "hash -> " << b.code << std::endl;
-
-        auto hash_ret = std::hash<uint64_t>()(b.code);
-
-        std::cout << "hash ret -> " << hash_ret << std::endl;
-
-        return b.code;
-    }
+namespace std {
+    template<>
+    struct hash<Analyse::backtrack_t> {
+        std::size_t operator()(const Analyse::backtrack_t &b) const {
+//            std::cout << "get hash: " << b.code << std::endl;
+            return std::hash<uint64_t>()(b.code);
+        }
+    };
 
-};
+    template<>
+    struct equal_to<Analyse::backtrack_t> {
+        bool operator()(const Analyse::backtrack_t &b1, const Analyse::backtrack_t &b2) const {
+//            std::cout << "get eq: " << b1.code << " ? " << b2.code << std::endl;
+            return b1.code == b2.code;
+        }
+    };
+}
 
 void Analyse::backtrack_demo(uint64_t code) {
 
-//    std::cout << RawCode(code) << std::endl;
-
     // TODO: confirm code exist
     std::cout << cases[code].step << std::endl;
 
 //    std::vector<std::unordered_set<backtrack_t>> dat;
 
-    auto b_hash = [](const backtrack_t &b) {
-        auto hash_dat = std::hash<uint64_t>()(b.code);
-        std::cout << "get hash: " << b.code << " -> " << hash_dat << std::endl;
-        return hash_dat;
-    };
-
-    auto b_eq = [](const backtrack_t &b1, const backtrack_t &b2) {
-        std::cout << "get eq: " << b1.code << " ? " << b2.code << std::endl;
-        return b1.code == b2.code;
-    };
-
-    std::unordered_set<backtrack_t, decltype(b_hash), decltype(b_eq)> test(0, b_hash, b_eq);
+    std::unordered_set<backtrack_t> test;
 
-//    test.emplace(backtrack_t {
-//        .code = 123,
-//        .layer_num = 0,
-//        .last = std::list<backtrack_t*>{},
-//        .next = std::list<backtrack_t*>{},
-//    });
-//
-//    test.emplace(backtrack_t {
-//        .code = 233,
-//        .layer_num = 1,
-//        .last = std::list<backtrack_t*>{},
-//        .next = std::list<backtrack_t*>{},
-//    });
-//
-//    test.emplace(backtrack_t {
-//        .code = 343,
-//        .layer_num = 2,
-//        .last = std::list<backtrack_t*>{},
-//        .next = std::list<backtrack_t*>{},
-//    });
 
     for (uint32_t i = 0; i < 20; ++i) {
         test.emplace(backtrack_t {
diff --git a/src/fast_cal/fast_cal.h b/src/fast_cal/fast_cal.h
index 955b264..314416c 100644
--- a/src/fast_cal/fast_cal.h
+++ b/src/fast_cal/fast_cal.h
@@ -8,6 +8,7 @@
 #include "core.h"
 #include "raw_code.h"
 
+// TODO: using prime number
 const uint32_t FC_MAP_RESERVE = 65536 * 8;
 
 /// FastCal not found -> return invalid raw code