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- // Copyright Louis Dionne 2013-2017
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
- template <typename ...xs>
- struct list { };
- template <typename T>
- struct basic_type { using type = T; };
- template <typename T>
- constexpr basic_type<T> type{};
- template <typename x, typename ...xs>
- constexpr auto head(list<x, xs...>)
- { return type<x>; }
- template <typename x, typename ...xs>
- constexpr auto tail(list<x, xs...>)
- { return list<xs...>{}; }
- template <typename F, typename State, typename X, typename ...Xs>
- constexpr auto foldl(F f, State s, list<X, Xs...> xs)
- { return foldl(f, f(s, head(xs)), tail(xs)); }
- template <typename F, typename State>
- constexpr auto foldl(F, State s, list<>)
- { return s; }
- //////////////////////////////////////////////////////////////////////////////
- struct f {
- template <typename ...>
- struct result { };
- template <typename X, typename Y>
- constexpr auto operator()(X, Y) const
- { return result<X, Y>{}; }
- };
- template <int> struct x { };
- struct state { };
- int main() {
- constexpr auto xs = list<
- <%= (1..input_size).map { |i| "x<#{i}>" }.join(', ') %>
- >{};
- constexpr auto result = foldl(f{}, state{}, xs);
- (void)result;
- }
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