4 files changed, 36 insertions, 6 deletions
diff --git a/include/erebos/frp.h b/include/erebos/frp.h
index 587d2b6..b60b29f 100644
--- a/include/erebos/frp.h
+++ b/include/erebos/frp.h
@@ -4,7 +4,6 @@
 #include <memory>
 #include <optional>
 #include <functional>
-#include <type_traits>
 #include <tuple>
 #include <variant>
 
@@ -115,6 +114,8 @@ public:
 		return impl->get(ctime, x);
 	}
 
+	template<typename C> BhvFun<A, C> lens() const;
+
 	const shared_ptr<BhvImpl<A, B>> impl;
 };
 
@@ -135,6 +136,8 @@ public:
 	}
 	Watched<A> watch(function<void(const A &)>);
 
+	template<typename C> BhvFun<monostate, C> lens() const;
+
 	const shared_ptr<BhvSource<A>> impl;
 };
 
@@ -227,4 +230,27 @@ BhvFun<A, C> operator>>(const BhvFun<A, B> & f, const BhvFun<B, C> & g)
 	return impl;
 }
 
+
+template<typename A, typename B>
+class BhvLens : public BhvImpl<A, B>
+{
+public:
+	B get(const BhvCurTime &, const A & x) const override
+	{ return A::template lens<B>(x); }
+};
+
+template<typename A, typename B>
+template<typename C>
+BhvFun<A, C> BhvFun<A, B>::lens() const
+{
+	return *this >> BhvFun<B, C>(make_shared<BhvLens<B, C>>());
+}
+
+template<typename A>
+template<typename C>
+BhvFun<monostate, C> BhvFun<monostate, A>::lens() const
+{
+	return *this >> BhvFun<A, C>(make_shared<BhvLens<A, C>>());
+}
+
 }
diff --git a/include/erebos/state.h b/include/erebos/state.h
index b1567b0..7060f22 100644
--- a/include/erebos/state.h
+++ b/include/erebos/state.h
@@ -32,6 +32,8 @@ public:
 	vector<Ref> sharedRefs() const;
 	LocalState sharedRefAdd(const Ref &) const;
 
+	template<typename T> static T lens(const LocalState &);
+
 private:
 	vector<Ref> lookupShared(UUID) const;
 	LocalState updateShared(UUID, const vector<Ref> &) const;
diff --git a/include/erebos/storage.h b/include/erebos/storage.h
index 2d00cc3..9d28ec7 100644
--- a/include/erebos/storage.h
+++ b/include/erebos/storage.h
@@ -182,8 +182,8 @@ public:
 	Ref & operator=(const Ref &) = default;
 	Ref & operator=(Ref &&) = default;
 
-	bool operator==(const Ref &) = delete;
-	bool operator!=(const Ref &) = delete;
+	bool operator==(const Ref &) const;
+	bool operator!=(const Ref &) const;
 
 	static std::optional<Ref> create(const Storage &, const Digest &);
 	static Ref zcreate(const Storage &);
diff --git a/include/erebos/sync.h b/include/erebos/sync.h
index 0b9ed9a..dad4e0e 100644
--- a/include/erebos/sync.h
+++ b/include/erebos/sync.h
@@ -6,9 +6,12 @@
 
 #include <optional>
 #include <mutex>
+#include <vector>
 
 namespace erebos {
 
+using std::vector;
+
 class SyncService : public Service
 {
 public:
@@ -22,11 +25,10 @@ public:
 
 private:
 	void peerWatcher(size_t, const class Peer *);
-	void localStateWatcher(const Head<LocalState> &);
+	void localStateWatcher(const vector<Ref> &);
 
 	const class Server * server;
-	std::mutex headMutex;
-	std::optional<WatchedHead<LocalState>> watchedHead;
+	std::optional<Watched<vector<Ref>>> watchedLocal;
 };
 
 }