signal: reduce templating complexity

signal.cpp

@@ -8,6 +8,3 @@
 
 
 #include "signal.hpp"
-
-// Instance something probably useful here so that we generate early compile/link errors.
-template class cruft::signal <void(void)>;

signal.hpp

@@ -18,45 +18,41 @@
 
 namespace cruft {
     namespace reduce {
-        template <typename FunctionT>
+        /// Returns the short-circuited logical-and of the results of all
+        /// connected callbacks.
         struct logical_and {
-            using result = typename func_traits<FunctionT>::return_type;
-
             template <typename InputT, typename ...Args>
-            result operator() (InputT first, InputT last, Args&&... args)
+            decltype(auto)
+            operator() (InputT first, InputT last, Args&&... args)
             {
                 while (first != last)
-                    if (!(*first++)(args...))
+                    if (!(std::invoke (*first++, args...)))
                         return false;
-
                 return true;
             }
         };
 
-        template <typename FunctionT>
+        /// Returns the short-circuited logical-or of the results of all
+        /// connected callbacks.
         struct logical_or {
-            using result = typename func_traits<FunctionT>::return_type;
-
             template <typename InputT, typename ...Args>
-            result operator() (InputT first, InputT last, Args&&... args)
+            decltype(auto)
+            operator() (InputT first, InputT last, Args&&... args)
             {
                 while (first != last)
-                    if ((*first++)(args...))
+                    if (std::invoke (*first++, args...))
                         return true;
-
                 return false;
             }
         };
 
-        template <typename FunctionT>
+        /// Unconditionally evaluates all connected callbacks. Returns nothing.
         struct noop {
-            using result = void;
-
             template <typename InputT, typename ...Args>
-            result operator() (InputT first, InputT last, Args&&... args)
+            void operator() (InputT first, InputT last, Args&&... args)
             {
                 while (first != last) {
-                    (*first++)(args...);
+                    std::invoke (*first++, args...);
                 }
             }
         };
@@ -64,14 +60,57 @@ namespace cruft {
 
     template <
         typename FunctionT,
-        template <typename> class ReductionT = reduce::noop
+        typename ReductionT = reduce::noop
     >
     class signal {
         public:
-            using result = typename ReductionT<FunctionT>::result;
+            using reduction_type = ReductionT;
-            using callback = std::function<FunctionT>;
+            using function_type = FunctionT;
 
-            struct cookie;
+            typedef std::list<FunctionT> group;
+
+            ///////////////////////////////////////////////////////////////////////
+            struct cookie {
+                cookie (cookie const&) = delete;
+                cookie& operator= (cookie const&) = delete;
+
+                cookie (typename group::iterator _position,
+                        signal<FunctionT,ReductionT> &_parent):
+                    m_position (_position),
+                    m_parent (_parent)
+                { ; }
+
+
+                cookie (cookie &&rhs) noexcept:
+                    m_position (rhs.m_position),
+                    m_parent   (rhs.m_parent)
+                {
+                    rhs.m_position = rhs.m_parent.m_children.end ();
+                }
+
+                cookie& operator= (cookie &&rhs) noexcept
+                {
+                    CHECK_EQ (&m_parent, &rhs.m_parent);
+                    std::swap (m_position, rhs.m_position);
+                    return *this;
+                }
+
+                ~cookie ()
+                {
+                    if (m_parent.m_children.end () != m_position)
+                        m_parent.disconnect (*this);
+                }
+
+
+                void reset (FunctionT &&cb)
+                {
+                    *m_position = std::move (cb);
+                }
+
+
+                typename group::iterator m_position;
+                signal<FunctionT,ReductionT> &m_parent;
+            };
 
         public:
             signal () = default;
@@ -81,7 +120,7 @@ namespace cruft {
             }
 
             /// Add a callback to list.
-            cookie connect [[nodiscard]] (callback &&_cb)
+            cookie connect [[nodiscard]] (FunctionT &&_cb)
             {
                 return cookie (
                     m_children.insert (
@@ -92,8 +131,7 @@ namespace cruft {
                 );
             }
 
-            cookie connect [[nodiscard]] (const callback &_cb)
+            cookie connect [[nodiscard]] (FunctionT const &_cb)
-            {
             {
                 return cookie (
                     m_children.insert (
@@ -103,7 +141,6 @@ namespace cruft {
                     *this
                 );
             }
-            }
 
             void disconnect (cookie &c)
             {
@@ -130,14 +167,10 @@ namespace cruft {
 
             /// Execute all callbacks
             template <typename ...ArgsT>
-            result
+            decltype(auto)
             operator() (ArgsT&&... tail)
             {
-                if (m_children.empty ())
+                return ReductionT {} (
-                    return result();
-
-                ReductionT<FunctionT> reducer;
-                return reducer (
                     m_children.begin (),
                     m_children.end (),
                     std::forward<ArgsT> (tail)...
@@ -145,49 +178,15 @@ namespace cruft {
             }
 
         private:
-            typedef std::list<callback> group;
             group m_children;
     };
 
 
-    ///////////////////////////////////////////////////////////////////////////
-    template <typename FunctionT, template <typename> class ReductionT>
-    struct signal<FunctionT,ReductionT>::cookie : public nocopy {
-        cookie (typename group::iterator _position,
-                signal<FunctionT,ReductionT> &_parent):
-            m_position (_position),
-            m_parent (_parent)
-        { ; }
-
-        cookie (cookie &&rhs):
-            m_position (rhs.m_position),
-            m_parent (rhs.m_parent)
-        {
-            rhs.m_position = rhs.m_parent.m_children.end ();
-        }
-
-        ~cookie ()
-        {
-            if (m_parent.m_children.end () != m_position)
-                m_parent.disconnect (*this);
-        }
-
-        void reset (callback &&cb)
-        {
-            *m_position = std::move (cb);
-        }
-
-        typename group::iterator m_position;
-        signal<FunctionT,ReductionT> &m_parent;
-    };
-
-
-
     ///////////////////////////////////////////////////////////////////////////
     // wrap a value in a signal and trigger on assignment
     //template <typename T, template <typename> class ReductionT>
-    template <typename ValueT>
+    template <typename ValueT, typename FunctionT = std::function<void(ValueT)>>
-    class value_signal : public signal<void(ValueT)> {
+    class value_signal : public signal<FunctionT> {
     public:
         explicit value_signal (ValueT _value): m_value (_value) { ; }
         value_signal () = default;

test/signal.cpp

@@ -9,7 +9,7 @@ void
 test_null (cruft::TAP::logger &tap)
 {
     tap.expect_nothrow ([] {
-        cruft::signal<void(void)> void_signal;
+        cruft::signal<void(*)(void)> void_signal;
         void_signal ();
     }, "void signal");
 }
@@ -28,7 +28,7 @@ void
 test_single (cruft::TAP::logger &tap)
 {
     unsigned int val = 0;
-    cruft::signal<void(unsigned int&)> void_signal;
+    cruft::signal<void(*)(unsigned int&)> void_signal;
 
     auto cookie = void_signal.connect (increment_uint);
     void_signal (val);
@@ -42,7 +42,7 @@ void
 test_double (cruft::TAP::logger &tap)
 {
     unsigned int val = 0;
-    cruft::signal<void(unsigned int&)> void_signal;
+    cruft::signal<void(*)(unsigned int&)> void_signal;
 
     auto cookie0 = void_signal.connect (increment_uint);
     auto cookie1 = void_signal.connect (increment_uint);
@@ -75,7 +75,7 @@ void
 test_combiner (cruft::TAP::logger &tap)
 {
     {
-        cruft::signal<bool(void), cruft::reduce::logical_and> sig;
+        cruft::signal<std::function<bool(void)>, cruft::reduce::logical_and> sig;
 
         unsigned count = 0;
         auto cookie0 = sig.connect ([&] (void) { ++count; return true; });
@@ -87,7 +87,7 @@ test_combiner (cruft::TAP::logger &tap)
     }
 
     {
-        cruft::signal<bool(void), cruft::reduce::logical_and> sig;
+        cruft::signal<std::function<bool(void)>, cruft::reduce::logical_and> sig;
 
         unsigned count = 0;
         auto cookie0 = sig.connect ([&] (void) { ++count; return true; });
@@ -109,12 +109,13 @@ void
 test_disconnect (cruft::TAP::logger &tap)
 {
     tap.expect_nothrow ([] {
-        cruft::signal<void(void)> sig;
+        using function_t = std::function<void(void)>;
+        cruft::signal<function_t> sig;
 
-        cruft::signal<void(void)>::cookie a = sig.connect ([&] (void) { sig.disconnect (a); });
+        cruft::signal<function_t>::cookie a = sig.connect ([&] (void) { sig.disconnect (a); });
-        cruft::signal<void(void)>::cookie b = sig.connect ([&] (void) { sig.disconnect (b); });
+        cruft::signal<function_t>::cookie b = sig.connect ([&] (void) { sig.disconnect (b); });
-        cruft::signal<void(void)>::cookie c = sig.connect ([&] (void) { sig.disconnect (c); });
+        cruft::signal<function_t>::cookie c = sig.connect ([&] (void) { sig.disconnect (c); });
-        cruft::signal<void(void)>::cookie d = sig.connect ([&] (void) { sig.disconnect (d); });
+        cruft::signal<function_t>::cookie d = sig.connect ([&] (void) { sig.disconnect (d); });
 
         sig ();
     }, "parallel disconnect in invocation");