Utils and tuple changes

include/utempl/tuple.hpp

@@ -23,7 +23,10 @@ struct TupleHelper<std::index_sequence<Is...>, Ts...> : public TupleLeaf<Is, Ts>
   inline constexpr TupleHelper(TTs&&... args) : 
     TupleLeaf<Is, Ts>{std::forward<TTs>(args)}... {};
   inline constexpr TupleHelper(const TupleHelper&) = default;
+  inline constexpr TupleHelper(TupleHelper&) = default;
   inline constexpr TupleHelper(TupleHelper&&) = default;
+  inline constexpr TupleHelper() :
+    TupleLeaf<Is, Ts>{}... {};
   inline constexpr bool operator==(const TupleHelper&) const = default;
 };
 
@@ -64,7 +67,9 @@ struct Tuple : public impl::TupleHelper<std::index_sequence_for<Ts...>, Ts...> {
     impl::TupleHelper<std::index_sequence_for<Ts...>, Ts...>(std::move(args)...) {};
   inline constexpr Tuple(const Tuple&) = default;
   inline constexpr Tuple(Tuple&&) = default;
-  
+  inline constexpr Tuple(Tuple&) = default;
+  inline constexpr Tuple() requires (sizeof...(Ts) != 0) : 
+    impl::TupleHelper<std::index_sequence_for<Ts...>, Ts...>() {};
   template <typename... TTs>
   inline constexpr bool operator==(const Tuple<TTs...>& other) const 
         requires (TypeList<Ts...>{} == TypeList<TTs...>{}) {

include/utempl/utils.hpp

@@ -111,41 +111,114 @@ inline constexpr auto Reverse(Tuple&& tuple) {
   }(std::make_index_sequence<kTupleSize<Tuple>>());
 };
 
+namespace impl {
+
+template <typename...>
+struct LeftFold;
+
+template <typename T>
+struct LeftFold<T> {
+  T data;
+};
+
+template <typename T, typename F>
+struct LeftFold<T, F> {
+  T data;
+  const F& f;
+  template <typename TT>
+  inline constexpr auto operator|(LeftFold<TT>&& other) {
+    using R = decltype(f(std::move(this->data), std::move(other.data)));
+    return LeftFold<R, F>{.data = f(std::move(this->data), std::move(other.data)), .f = this->f};
+  };
+};
+
+
+
+} // namespace impl
+
+
+template <TupleLike Tuple, typename T, typename F>
+inline constexpr auto LeftFold(Tuple&& tuple, T&& init, F&& f) {
+  return [&]<auto... Is>(std::index_sequence<Is...>){
+    return (
+      impl::LeftFold<std::remove_cvref_t<T>, std::remove_cvref_t<F>>{.data = std::forward<T>(init), .f = std::forward<F>(f)} 
+      | ...
+      | impl::LeftFold<std::remove_cvref_t<decltype(Get<Is>(tuple))>>{.data = Get<Is>(tuple)}
+    ).data;
+  }(std::make_index_sequence<kTupleSize<Tuple>>());
+};
+
+
+
 template <TupleLike Tuple, TupleLike Tuple2>
 inline constexpr auto TupleCat(Tuple&& tuple, Tuple2&& tuple2) {
   return [&]<auto... Is, auto... IIs>(std::index_sequence<Is...>, std::index_sequence<IIs...>){
     return MakeTuple<Tuple>(Get<Is>(tuple)..., Get<IIs>(tuple2)...);
   }(std::make_index_sequence<kTupleSize<Tuple>>(), std::make_index_sequence<kTupleSize<Tuple2>>());
 };
-namespace impl {
-template <TupleLike Tuple>
-struct TupleCater {
-  Tuple tuple;
-  template <TupleLike Other>
-  inline constexpr auto operator+(TupleCater<Other>&& other) {
-    using ResultType = decltype(TupleCat(std::move(this->tuple), other.tuple));
-    return TupleCater<ResultType>{TupleCat(std::move(this->tuple), std::move(other.tuple))};
-  };
-};
-} // namespace impl
 
 template <TupleLike... Tuples>
-inline constexpr auto TupleCat(Tuples&&... tuples) {
-  return (impl::TupleCater{std::forward<Tuples>(tuples)} + ...).tuple;
+inline constexpr auto TupleCat(Tuples&&... tuples) requires (sizeof...(tuples) >= 1) {
+  return LeftFold(
+    Tuple{std::forward<Tuples>(tuples)...},
+    MakeTuple<decltype(Arg<0>(std::forward<Tuples>(tuples)...))>(),
+    []<TupleLike Tup, TupleLike Tup2>(Tup&& tup, Tup2&& tup2){
+      return TupleCat(std::forward<Tup>(tup), std::forward<Tup2>(tup2));
+    });
 };
+template <typename... Ts>
+inline constexpr auto Tie(Ts&... args) -> Tuple<Ts&...> {
+  return {args...};
+};
+
+template <template <typename...> typename F, TupleLike Tuple>
+inline constexpr bool kEveryElement = 
+  []<auto... Is>(std::index_sequence<Is...>){
+    return (F<decltype(Get<Is>(std::declval<Tuple>()))>::value && ...);
+  }(std::make_index_sequence<kTupleSize<Tuple>>());
+
+template <template <typename...> typename F, typename... Ts>
+struct PartialCaller {
+  template <typename... TTs>
+  using type = F<Ts..., TTs...>;
+};
+template <template <typename...> typename F, typename... Ts>
+consteval auto PartialCallerF(TypeList<Ts...>) {
+  return []<typename... TTs>(TypeList<TTs...>){
+    return F<Ts..., TTs...>{};
+  };
+};
+
+
+
+template <TupleLike Tuple, typename T>
+inline constexpr auto FirstOf(Tuple&& tuple, T&& init) requires kEveryElement<std::is_invocable, Tuple> {
+  return LeftFold(
+    std::forward<Tuple>(tuple),
+    std::forward<T>(init),
+    []<typename TT, typename F>(TT&& value, F&& f) -> TT {
+      if(value) {
+        return value;
+      };
+      return f();
+    }
+  );
+};
+
 
 template <TupleLike Tuple>
 inline constexpr auto Filter(Tuple&& tuple, auto&& f) {
-  return [&]<auto... Is>(std::index_sequence<Is...>){
-    return TupleCat([&]<auto I>(Wrapper<I>){
-      constexpr bool flag = decltype(f(Get<I>(tuple)))::kValue;
-      if constexpr(flag) {
-        return MakeTuple<Tuple>(Get<I>(tuple));
+  return LeftFold(
+    std::forward<Tuple>(tuple),
+    MakeTuple<Tuple>(),
+    [&]<TupleLike Accumulator, typename T>(Accumulator&& accumulator, T&& add) {
+      if constexpr(decltype(f(std::forward<T>(add))){}) {
+        return TupleCat(std::forward<Accumulator>(accumulator), std::forward<T>(add));
       } else {
-        return MakeTuple<Tuple>();
+        return accumulator;
       };
-    }(Wrapper<Is>{})...);
-  }(std::make_index_sequence<kTupleSize<Tuple>>());
+    }
+  );
 };
 
-};
+} // namespace utempl