let_each.h

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#pragma once
 
#include "di/execution/algorithm/let.h"
#include "di/execution/concepts/sender.h"
#include "di/execution/sequence/sequence_sender.h"
#include "di/execution/sequence/transform_each.h"
#include "di/function/curry_back.h"
#include "di/function/tag_invoke.h"
#include "di/meta/util.h"
 
namespace di::execution {
namespace let_each_ns {
    struct ValueFunction {
        template<concepts::Sender Seq, concepts::MovableValue Fun>
        auto operator()(Seq&& sequence, Fun&& transformer) const -> concepts::SequenceSender auto {
            if constexpr (concepts::TagInvocable<ValueFunction, Seq, Fun>) {
                return function::tag_invoke(*this, util::forward<Seq>(sequence), util::forward<Fun>(transformer));
            } else {
                return transform_each(util::forward<Seq>(sequence), let_value(util::forward<Fun>(transformer)));
            }
        }
    };
 
    struct ErrorFunction {
        template<concepts::Sender Seq, concepts::MovableValue Fun>
        auto operator()(Seq&& sequence, Fun&& transformer) const -> concepts::SequenceSender auto {
            if constexpr (concepts::TagInvocable<ErrorFunction, Seq, Fun>) {
                return function::tag_invoke(*this, util::forward<Seq>(sequence), util::forward<Fun>(transformer));
            } else {
                return transform_each(util::forward<Seq>(sequence), let_error(util::forward<Fun>(transformer)));
            }
        }
    };
 
    struct StoppedFunction {
        template<concepts::Sender Seq, concepts::MovableValue Fun>
        auto operator()(Seq&& sequence, Fun&& transformer) const -> concepts::SequenceSender auto {
            if constexpr (concepts::TagInvocable<StoppedFunction, Seq, Fun>) {
                return function::tag_invoke(*this, util::forward<Seq>(sequence), util::forward<Fun>(transformer));
            } else {
                return transform_each(util::forward<Seq>(sequence), let_stopped(util::forward<Fun>(transformer)));
            }
        }
    };
}

constexpr inline auto let_value_each = function::curry_back(let_each_ns::ValueFunction {}, meta::c_<2ZU>);

constexpr inline auto let_error_each = function::curry_back(let_each_ns::ErrorFunction {}, meta::c_<2ZU>);

constexpr inline auto let_stopped_each = function::curry_back(let_each_ns::StoppedFunction {}, meta::c_<2ZU>);
}