Created
October 17, 2020 19:32
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std::tuple map and foldl
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// c++17 | |
#pragma once | |
#include <tuple> | |
#include <utility> | |
namespace detail { | |
template<class T, class F, size_t ...N> | |
auto constexpr tuple_map_impl(const T &t, F &&f, std::index_sequence<N...>) { | |
return std::make_tuple(std::forward<F>(f)(std::get<N>(t))...); | |
} | |
template<size_t cnt, class T, class T1, class F> | |
auto constexpr tuple_reduce_impl(const T &t, F &&f, T1 &&acc) { | |
if constexpr (cnt == std::tuple_size_v<T>) | |
return acc; | |
else | |
return tuple_reduce_impl<cnt+1>(t, std::forward<F>(f), | |
std::forward<F>(f)(std::forward<T1>(acc), std::get<cnt>(t))); | |
} | |
} | |
template<class T, class F> | |
auto constexpr tuple_map(const T &t, F &&f) { | |
auto constexpr sz = std::tuple_size_v<T>; | |
return detail::tuple_map_impl(t, std::forward<F>(f), std::make_index_sequence<sz>{}); | |
} | |
template<class T, class F> | |
auto constexpr tuple_reduce(const T &t, F &&f) { | |
return detail::tuple_reduce_impl<1>(t, std::forward<F>(f), std::get<0>(t)); | |
} | |
template<class T, class F, class InitT> | |
auto constexpr tuple_reduce(const T &t, F &&f, InitT &&init) { | |
return detail::tuple_reduce_impl<0>(t, std::forward<F>(f), std::forward<InitT>(init)); | |
} | |
//auto v = std::make_tuple(1,2,3,4.4,4.4); | |
//auto vm = tuple_map(v, [](auto x) {return x+1;}); | |
//std::cout << std::get<0>(vm) << std::endl; // 2 | |
//std::cout << tuple_reduce(v, [](auto x, auto y){return x+y;}) << std::endl; // 14.8 | |
// std::cout << tuple_reduce(v, [](auto x, auto y){return x+y;}, 0) << std::endl; // 14.8 |
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