diff --git a/develop/matchit.h b/develop/matchit.h
new file mode 100644
index 0000000..e785ebe
--- /dev/null
+++ b/develop/matchit.h
@@ -0,0 +1,6 @@
+// Replace include/matchit.h with this file when developing.
+
+#include "../develop/matchit/core.h"
+#include "../develop/matchit/expression.h"
+#include "../develop/matchit/patterns.h"
+#include "../develop/matchit/utility.h"
diff --git a/develop/matchit/patterns.h b/develop/matchit/patterns.h
index 597504e..4a4029c 100644
--- a/develop/matchit/patterns.h
+++ b/develop/matchit/patterns.h
@@ -214,6 +214,22 @@ namespace matchit
         static_assert(std::is_same_v<decayArrayT<int32_t const[]>, int32_t const *>);
         static_assert(std::is_same_v<decayArrayT<int32_t const &>, int32_t const &>);
 
+        template <typename T>
+        struct AddConstToPointer
+        {
+            using type = std::conditional_t<
+                !std::is_pointer_v<T>, T,
+                std::add_pointer_t<std::add_const_t<std::remove_pointer_t<T>>>>;
+        };
+        template <typename T>
+        using AddConstToPointerT = typename AddConstToPointer<T>::type;
+
+        static_assert(std::is_same_v<AddConstToPointerT<void *>, void const *>);
+        static_assert(std::is_same_v<AddConstToPointerT<int32_t>, int32_t>);
+
+        template <typename Pattern>
+        using InternalPatternT = std::remove_reference_t<AddConstToPointerT<decayArrayT<Pattern>>>;
+
         template <typename Pattern>
         class PatternTraits;
 
@@ -310,7 +326,7 @@ namespace matchit
 
         private:
             Pattern const mPattern;
-            Func const mHandler;
+            std::conditional_t<std::is_function_v<Func>, Func const &, Func const> mHandler;
         };
 
         template <typename Pattern, typename Pred>
@@ -439,7 +455,7 @@ namespace matchit
             constexpr auto const &patterns() const { return mPatterns; }
 
         private:
-            std::tuple<Patterns...> mPatterns;
+            std::tuple<InternalPatternT<Patterns>...> mPatterns;
         };
 
         template <typename... Patterns>
@@ -530,7 +546,7 @@ namespace matchit
 
         private:
             Unary const mUnary;
-            Pattern const mPattern;
+            InternalPatternT<Pattern> const mPattern;
         };
 
         template <typename Unary, typename Pattern>
@@ -602,7 +618,7 @@ namespace matchit
             constexpr auto const &patterns() const { return mPatterns; }
 
         private:
-            std::tuple<Patterns...> mPatterns;
+            std::tuple<InternalPatternT<Patterns>...> mPatterns;
         };
 
         template <typename... Patterns>
@@ -681,7 +697,7 @@ namespace matchit
             auto const &pattern() const { return mPattern; }
 
         private:
-            Pattern mPattern;
+            InternalPatternT<Pattern> mPattern;
         };
 
         template <typename Pattern>
@@ -944,22 +960,7 @@ namespace matchit
             constexpr explicit Ds(Patterns const &...patterns) : mPatterns{patterns...} {}
             constexpr auto const &patterns() const { return mPatterns; }
 
-        private:
-            template <typename T>
-            struct AddConstToPointer
-            {
-                using type = std::conditional_t<
-                    !std::is_pointer_v<T>, T,
-                    std::add_pointer_t<std::add_const_t<std::remove_pointer_t<T>>>>;
-            };
-            template <typename T>
-            using AddConstToPointerT = typename AddConstToPointer<T>::type;
-
-            static_assert(std::is_same_v<AddConstToPointerT<void *>, void const *>);
-            static_assert(std::is_same_v<AddConstToPointerT<int32_t>, int32_t>);
-
-        public:
-            using Type = std::tuple<AddConstToPointerT<decayArrayT<Patterns>>...>;
+            using Type = std::tuple<InternalPatternT<Patterns>...>;
 
         private:
             Type mPatterns;
diff --git a/develop/matchit/utility.h b/develop/matchit/utility.h
index 497c42e..ce98ad6 100644
--- a/develop/matchit/utility.h
+++ b/develop/matchit/utility.h
@@ -91,17 +91,19 @@ namespace matchit
           { return false; });
     }
 
-    constexpr auto dsVia = [](auto &&...members)
+    constexpr auto dsVia = [](auto ...members)
     {
-      return [members...](auto &&...pats)
+      return [members...](auto ...pats)
       { return and_(app(members, pats)...); };
     };
 
     template <typename T>
-    constexpr auto asDsVia = [](auto &&...members)
+    constexpr auto asDsVia = [](auto ...members)
     {
-      return [members...](auto &&...pats)
+      return [members...](auto ...pats)
       {
+        // FIXME, why the following line will cause segfault in at-Bindings.cpp
+        // return as<T>(dsVia(members...)(pats...));
         return as<T>(and_(app(members, pats)...));
       };
     };
diff --git a/include/matchit.h b/include/matchit.h
index a096394..29bcebb 100644
--- a/include/matchit.h
+++ b/include/matchit.h
@@ -521,6 +521,22 @@ namespace matchit
         static_assert(std::is_same_v<decayArrayT<int32_t const[]>, int32_t const *>);
         static_assert(std::is_same_v<decayArrayT<int32_t const &>, int32_t const &>);
 
+        template <typename T>
+        struct AddConstToPointer
+        {
+            using type = std::conditional_t<
+                !std::is_pointer_v<T>, T,
+                std::add_pointer_t<std::add_const_t<std::remove_pointer_t<T>>>>;
+        };
+        template <typename T>
+        using AddConstToPointerT = typename AddConstToPointer<T>::type;
+
+        static_assert(std::is_same_v<AddConstToPointerT<void *>, void const *>);
+        static_assert(std::is_same_v<AddConstToPointerT<int32_t>, int32_t>);
+
+        template <typename Pattern>
+        using InternalPatternT = std::remove_reference_t<AddConstToPointerT<decayArrayT<Pattern>>>;
+
         template <typename Pattern>
         class PatternTraits;
 
@@ -617,7 +633,7 @@ namespace matchit
 
         private:
             Pattern const mPattern;
-            std::conditional_t<std::is_function_v<Func>, Func const&, Func const> mHandler;
+            std::conditional_t<std::is_function_v<Func>, Func const &, Func const> mHandler;
         };
 
         template <typename Pattern, typename Pred>
@@ -746,7 +762,7 @@ namespace matchit
             constexpr auto const &patterns() const { return mPatterns; }
 
         private:
-            std::tuple<Patterns...> mPatterns;
+            std::tuple<InternalPatternT<Patterns>...> mPatterns;
         };
 
         template <typename... Patterns>
@@ -837,7 +853,7 @@ namespace matchit
 
         private:
             Unary const mUnary;
-            Pattern const mPattern;
+            InternalPatternT<Pattern> const mPattern;
         };
 
         template <typename Unary, typename Pattern>
@@ -909,7 +925,7 @@ namespace matchit
             constexpr auto const &patterns() const { return mPatterns; }
 
         private:
-            std::tuple<Patterns...> mPatterns;
+            std::tuple<InternalPatternT<Patterns>...> mPatterns;
         };
 
         template <typename... Patterns>
@@ -988,7 +1004,7 @@ namespace matchit
             auto const &pattern() const { return mPattern; }
 
         private:
-            Pattern mPattern;
+            InternalPatternT<Pattern> mPattern;
         };
 
         template <typename Pattern>
@@ -1251,22 +1267,7 @@ namespace matchit
             constexpr explicit Ds(Patterns const &...patterns) : mPatterns{patterns...} {}
             constexpr auto const &patterns() const { return mPatterns; }
 
-        private:
-            template <typename T>
-            struct AddConstToPointer
-            {
-                using type = std::conditional_t<
-                    !std::is_pointer_v<T>, T,
-                    std::add_pointer_t<std::add_const_t<std::remove_pointer_t<T>>>>;
-            };
-            template <typename T>
-            using AddConstToPointerT = typename AddConstToPointer<T>::type;
-
-            static_assert(std::is_same_v<AddConstToPointerT<void *>, void const *>);
-            static_assert(std::is_same_v<AddConstToPointerT<int32_t>, int32_t>);
-
-        public:
-            using Type = std::tuple<AddConstToPointerT<decayArrayT<Patterns>>...>;
+            using Type = std::tuple<InternalPatternT<Patterns>...>;
 
         private:
             Type mPatterns;
@@ -2023,17 +2024,19 @@ namespace matchit
           { return false; });
     }
 
-    constexpr auto dsVia = [](auto &&...members)
+    constexpr auto dsVia = [](auto ...members)
     {
-      return [members...](auto &&...pats)
+      return [members...](auto ...pats)
       { return and_(app(members, pats)...); };
     };
 
     template <typename T>
-    constexpr auto asDsVia = [](auto &&...members)
+    constexpr auto asDsVia = [](auto ...members)
     {
-      return [members...](auto &&...pats)
+      return [members...](auto ...pats)
       {
+        // FIXME, why the following line will cause segfault in at-Bindings.cpp
+        // return as<T>(dsVia(members...)(pats...));
         return as<T>(and_(app(members, pats)...));
       };
     };
diff --git a/sample/CMakeLists.txt b/sample/CMakeLists.txt
index 2ed2e75..3200e13 100644
--- a/sample/CMakeLists.txt
+++ b/sample/CMakeLists.txt
@@ -49,6 +49,7 @@ Predicate-based-Discriminator
 Closed-Class-Hierarchy
 Matcher-within
 visit
+graph
 )
 
 foreach(sample ${MATCHIT_SAMPLES})
diff --git a/sample/graph.cpp b/sample/graph.cpp
new file mode 100644
index 0000000..b91d0a8
--- /dev/null
+++ b/sample/graph.cpp
@@ -0,0 +1,57 @@
+#include "matchit.h"
+#include <iostream>
+#include <memory>
+#include <vector>
+#include <string>
+
+template <typename T>
+struct Node
+{
+  T value;
+  std::vector<Node *> parents;
+};
+
+/*
+  A
+  |
+  B
+  | \
+  |  C
+  | /
+  D
+*/
+
+bool matchGraph()
+{
+  using StrNode = Node<std::string>;
+  auto A = std::make_unique<StrNode>(StrNode{"A", {}});
+  auto B = std::make_unique<StrNode>(StrNode{"B", {A.get()}});
+  auto C = std::make_unique<StrNode>(StrNode{"C", {B.get()}});
+  auto D = std::make_unique<StrNode>(StrNode{"D", {B.get(), C.get()}});
+
+  using namespace matchit;
+  // FIXME, moving dsN into someDsN will cause segfault.
+  constexpr auto dsN = dsVia(&StrNode::value, &StrNode::parents);
+  constexpr auto someDsN = [dsN](auto... pats)
+  {
+    return some(dsN(pats...));
+  };
+  Id<StrNode *> b;
+  return match(D)(
+      pattern | someDsN("D",
+                        ds(
+                            b.at(
+                                someDsN("B",
+                                         ds(someDsN("A", ds())))),
+                            someDsN("C", ds(b)))) = []
+      {
+        std::cout << "Matched!" << std::endl;
+        return true;
+      });
+}
+
+int main()
+{
+  assert(matchGraph());
+  return 0;
+}
\ No newline at end of file