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Commit 7e1f955

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author
ecrypa
committed
implement min_element (guarded for SFINAE)
1 parent ebda810 commit 7e1f955

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3 files changed

+235
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3 files changed

+235
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‎example/src/list.cpp

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@@ -677,4 +677,187 @@ IS_SAME(
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);
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/// [accumulate]
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)
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HIDE(
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/// [min_element]
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using nums = metal::numbers<4, 42, 17, -7, 0>;
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using comp_lt = metal::lambda<metal::less>;
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IS_SAME(metal::min_element<nums, comp_lt>, metal::number<-7>);
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using comp_gt = metal::lambda<metal::greater>;
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IS_SAME(metal::min_element<nums, comp_gt>, metal::number<42>);
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using vals = metal::list<const char[3], char[1], char[1], char[3], const char[1]>;
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template<typename x, typename y>
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using smaller = metal::number<(sizeof(x) < sizeof(y))>;
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IS_SAME(metal::min_element<vals, metal::lambda<smaller>>, char[1]);
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template<typename x, typename y>
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using larger = metal::number<(sizeof(x) > sizeof(y))>;
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IS_SAME(metal::min_element<vals, metal::lambda<larger>>, const char[3]);
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/// [min_element]
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)
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HIDE(
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template<template<class...> class tmpl, class... args>
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using is_sfinae_friendly = metal::is_invocable<metal::lambda<tmpl>, args...>;
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using some_extra_argument = int;
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using attempt_to_instantiate = is_sfinae_friendly<
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metal::detail::_min_element<metal::lambda<std::is_void>>::template combiner,
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void, some_extra_argument, char
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>;
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)
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HIDE(
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template<class, class>
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using good_comp = metal::false_;
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static_assert(
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metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<good_comp>
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>{}, "");
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)
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HIDE(
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template<class...>
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using good_comp = metal::false_;
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static_assert(
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metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<good_comp>
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>{}, "");
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)
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HIDE(
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template<class, class...>
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using good_comp = metal::false_;
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static_assert(
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metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<good_comp>
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>{}, "");
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)
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HIDE(
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template<class, class>
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struct good_lazy_comp {
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using type = metal::false_;
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};
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template<class... args>
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using good_comp = typename good_lazy_comp<args...>::type;
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static_assert(
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metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<good_comp>
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>{}, "");
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)
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HIDE(
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template<class, class, class...>
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struct good_lazy_comp {
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template<class...>
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using type = metal::false_;
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};
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template<class... args>
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using good_comp = typename good_lazy_comp<args...>::template type<args...>;
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static_assert(
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metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<good_comp>
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>{}, "");
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)
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HIDE(
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template<class>
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struct bad_lazy_comp {
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using type = metal::false_;
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};
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template<class... args>
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using bad_comp = typename bad_lazy_comp<args...>::type;
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static_assert(
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!metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<bad_comp>
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>{}, "");
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)
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HIDE(
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template<class>
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using bad_comp = metal::false_;
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static_assert(
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!metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<bad_comp>
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>{}, "");
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)
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HIDE(
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template<class, class, class>
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using bad_comp = metal::false_;
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static_assert(
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!metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<bad_comp>
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>{}, "");
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)
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HIDE(
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template<class, class, class, class...>
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using bad_comp = metal::false_;
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static_assert(
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!metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<bad_comp>
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>{}, "");
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)
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HIDE(
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template<class, class>
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struct bad_comp;
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static_assert(
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!metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<bad_comp>
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>{}, "");
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)
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HIDE(
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template<class, class>
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struct bad_comp {};
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static_assert(
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!metal::is_invocable<
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metal::lambda<metal::min_element>,
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metal::numbers<4, 42, 17, -7, 0>,
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metal::lambda<bad_comp>
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>{}, "");
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)
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#endif

‎include/metal/list.hpp

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@@ -28,6 +28,7 @@
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#include "list/iota.hpp"
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#include "list/join.hpp"
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#include "list/list.hpp"
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#include "list/min_element.hpp"
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#include "list/none_of.hpp"
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#include "list/partition.hpp"
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#include "list/powerset.hpp"

‎include/metal/list/min_element.hpp

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#ifndef METAL_LIST_MIN_ELEMENT_HPP
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#define METAL_LIST_MIN_ELEMENT_HPP
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#include "../config.hpp"
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#include "../lambda/apply.hpp"
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#include "../lambda/lambda.hpp"
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#include "../lambda/partial.hpp"
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#include "../number/if.hpp"
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#include "../value/fold_left.hpp"
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namespace metal {
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namespace detail {
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template<bool>
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struct _min_element_binary_expr_guard {
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template<template<class...> class expr, class a, class b>
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using type = expr<a, b>;
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};
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template<class...>
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struct _guard { // alternate version for arity n, but possibly(?) slower
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template<template<class...> class expr, class... args>
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using type = expr<args...>;
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};
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template<typename lbd>
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struct _min_element {};
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template<template<class...> class expr>
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struct _min_element<lambda<expr>> {
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template<class x, class y, class... empty>
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using combiner =
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if_<typename _min_element_binary_expr_guard<!sizeof...(
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empty)>::template type<expr, y, x>,
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y, x>;
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template<class x, class y, class... _>
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using more_general_but_possibly_slower_combiner = // TODO: benchmark
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if_<typename _guard<_...>::template type<expr, y, x>, y, x>;
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template<class seq>
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using type =
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apply<partial<lambda<fold_left>, lambda<combiner>>, seq>;
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};
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} // detail
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template<typename seq, typename lbd>
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using min_element = typename detail::_min_element<lbd>::template type<seq>;
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} // metal
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#endif

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