add find method to containers to make fast lookups into set/unordered_set

docs/source/api/containers.rst

@@ -76,7 +76,7 @@ Based on the type pushed, a few additional functions are added as "member functi
 * ``my_container:clear()``: This will call the underlying containers ``clear`` function.
 * ``my_container:add( key, value )`` or ``my_container:add( value )``: this will add to the end of the container, or if it is an associative or ordered container, simply put in an expected key-value pair into it.
 * ``my_contaner:insert( where, value )`` or ``my_contaner:insert( key, value )``: similar to add, but it only takes two arguments. In the case of ``std::vector`` and the like, the first argument is a ``where`` integer index. The second argument is the value. For associative containers, a key and value argument are expected.
-
+* ``my_container:find( value )``: This will call the underlying containers ``find`` function if it exists, or in case of associative containers, it will work just like an index call. This is meant to give a fast membership check for ``std::set`` and ``std::unordered_set`` containers.
 
 .. _container-detection:
 

sol/container_usertype_metatable.hpp

@@ -34,7 +34,7 @@ namespace sol {
 			typedef std::array<char, 1> one;
 			typedef std::array<char, 2> two;
 
-			template <typename C> static one test(decltype(&C::find));
+			template <typename C> static one test(decltype(std::declval<C>().find(std::declval<std::add_rvalue_reference_t<typename C::value_type>>()))*);
 			template <typename C> static two test(...);
 
 		public:
@@ -159,6 +159,9 @@ namespace sol {
 					else if (name == "clear") {
 						return stack::push(L, &clear_call);
 					}
+					else if (name == "find") {
+						return stack::push(L, &find_call);
+					}
 				}
 			}
 			return stack::push(L, lua_nil);
@@ -191,6 +194,9 @@ namespace sol {
 					else if (name == "clear") {
 						return stack::push(L, &clear_call);
 					}
+					else if (name == "find") {
+						return stack::push(L, &find_call);
+					}
 				}
 			}
 
@@ -392,6 +398,36 @@ namespace sol {
 			return real_clear_call_capable(std::integral_constant<bool, detail::has_clear<T>::value>(), L);
 		}
 
+		static int real_find_call_capable(std::false_type, std::false_type, lua_State*L) {
+			static const std::string& s = detail::demangle<T>();
+			return luaL_error(L, "sol: cannot call find on type %s", s.c_str());
+		}
+
+		static int real_find_call_capable(std::false_type, std::true_type, lua_State*L) {
+			return real_index_call(L);
+		}
+
+		static int real_find_call_capable(std::true_type, std::false_type, lua_State* L) {
+			auto k = stack::check_get<V>(L, 2);
+			if (k) {
+				auto& src = get_src(L);
+				auto it = src.find(*k);
+				if (it != src.end()) {
+					auto& v = *it;
+					return stack::push_reference(L, v);
+				}
+			}
+			return stack::push(L, lua_nil);
+		}
+
+		static int real_find_call_capable(std::true_type, std::true_type, lua_State* L) {
+			return real_index_call(L);
+		}
+
+		static int real_find_call(lua_State*L) {
+			return real_find_call_capable(std::integral_constant<bool, detail::has_find<T>::value>(), is_associative(), L);
+		}
+
 		static int add_call(lua_State*L) {
 			return detail::static_trampoline<(&real_add_call)>(L);
 		}
@@ -404,6 +440,10 @@ namespace sol {
 			return detail::static_trampoline<(&real_clear_call)>(L);
 		}
 
+		static int find_call(lua_State*L) {
+			return detail::static_trampoline<(&real_find_call)>(L);
+		}
+
 		static int length_call(lua_State*L) {
 			return detail::static_trampoline<(&real_length_call)>(L);
 		}
@@ -430,7 +470,7 @@ namespace sol {
 			template <typename T>
 			inline auto container_metatable() {
 				typedef container_usertype_metatable<std::remove_pointer_t<T>> meta_cumt;
-				std::array<luaL_Reg, 10> reg = { {
+				std::array<luaL_Reg, 11> reg = { {
 					{ "__index", &meta_cumt::index_call },
 					{ "__newindex", &meta_cumt::new_index_call },
 					{ "__pairs", &meta_cumt::pairs_call },
@@ -439,6 +479,7 @@ namespace sol {
 					{ "clear", &meta_cumt::clear_call },
 					{ "insert", &meta_cumt::insert_call },
 					{ "add", &meta_cumt::add_call },
+					{ "find", &meta_cumt::find_call },
 					std::is_pointer<T>::value ? luaL_Reg{ nullptr, nullptr } : luaL_Reg{ "__gc", &detail::usertype_alloc_destroy<T> },
 					{ nullptr, nullptr }
 				} };

test_containers.cpp

@@ -289,6 +289,11 @@ end
 function i (x)
 	x:clear()
 end
+
+function sf (x,v)
+	return x:find(v)
+end
+
 )");
 
 	// Have the function we 
@@ -296,6 +301,7 @@ end
 	sol::function g = lua["g"];
 	sol::function h = lua["h"];
 	sol::function i = lua["i"];
+	sol::function sf = lua["sf"];
 
 	// Set a global variable called 
 	// "arr" to be a vector of 5 lements
@@ -316,6 +322,12 @@ end
 	REQUIRE(map.size() == 6);
 	REQUIRE(set.size() == 6);
 
+	int r = sf(set, 8);
+	REQUIRE(r == 8);
+
+	sol::object rn = sf(set, 9);
+	REQUIRE(rn == sol::nil);
+
 	i(lua["arr"]);
 	i(lua["map"]);
 	i(lua["set"]);