coord/ops: add elementwise apply

coord/ops.hpp

@@ -25,6 +25,7 @@
 
 #include "../debug.hpp"
 #include "../maths.hpp"
+#include "../tuple.hpp"
 #include "../preprocessor.hpp"
 #include "../types/bits.hpp"
 
@@ -473,45 +474,77 @@ namespace util {
 
 
     ///////////////////////////////////////////////////////////////////////////
-    // logic operators
     namespace detail {
+        /// invoke a function elementwise to the arguments elementwise.
+        ///
+        /// \tparam ArgsT a tuple containing the (coord) arguments for the func
         template <
             typename RetT,
-            typename ArgT,
             typename FuncT,
-            std::size_t ...Indices,
+            typename ArgsT,
-            typename = std::enable_if_t<
+            std::size_t ...Indices
-                is_coord_v<ArgT> && is_coord_v<RetT>, void
-            >
         >
         constexpr auto
         apply (const std::index_sequence<Indices...>,
                FuncT &&func,
-               const ArgT &a,
+               ArgsT args) noexcept
-               const ArgT &b)
         {
+            using part_t = std::tuple_element_t<0,ArgsT>;
+            using value_t = typename part_t::value_type;
+
             return RetT {
-                std::invoke (func, a[Indices], b[Indices])...
+                std::apply (
+                    func,
+                    ::util::tuple::convert (
+                        static_cast<
+                            const value_t& (&)(const part_t&)
+                        > (
+                                get<Indices,RetT>
+                        ), args
+                    )
+                )...
             };
         }
     }
 
 
+    //-------------------------------------------------------------------------
+    // invokes a function elementwise using elementwise parameters from the
+    // supplied arguments.
+    //
+    // equivalent to this pseduocode:
+    //   for (int i: indices (ReturnT))
+    //       res[i] = func (args[i]...);
+    //   return res;
+    //
+    // forwards the arguments as a tuple to a helper function that has access
+    // to indices as a template parameter.
     template <
-        typename RetT,
+        typename ReturnT,
-        std::size_t S,
-        typename T,
-        template <std::size_t,typename> class ArgT,
         typename FuncT,
+        typename ...ArgT,
         typename = std::enable_if_t<
-            is_coord_v<RetT> && is_coord_v<ArgT>, void
+            // return type and arguments must be coordinates
+            (is_coord_v<ReturnT> && ... && is_coord_v<std::decay_t<ArgT>>) &&
+            // all types must be the same arity
+            ((ReturnT::elements == std::decay_t<ArgT>::elements) && ...) &&
+            // all the arguments must be the same type
+            (std::is_same_v<
+                 std::tuple_element_t<0,std::tuple<std::decay_t<ArgT>...>>,
+                 std::decay_t<ArgT>
+             > && ...),
+            void
         >,
-        typename Indices = std::make_index_sequence<S>
+        typename Indices = std::make_index_sequence<ReturnT::elements>
     >
     constexpr auto
-    apply (FuncT &&func, const ArgT<S,T> &a, const ArgT<S,T> &b)
+    invoke (FuncT &&func, ArgT &&...args) noexcept
     {
-        return detail::apply (Indices{}, std::forward<FuncT> (func), a, b);
+        return detail::apply<ReturnT> (
+            Indices{},
+            std::forward<FuncT> (func),
+            std::tuple (std::forward<ArgT> (args)...)
+        );
     }