lagoon/range/fold.hpp

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#ifndef LAGOON_RANGE_ACCUMULATE_1011291729_HPP
#define LAGOON_RANGE_ACCUMULATE_1011291729_HPP

#include <lagoon/lagoon_fwd.hpp>

LAGOON_NAMESPACE_BEGIN


template <typename State, class Range, typename BinaryOp>
State fold(Range range, State state, BinaryOp op)
{
    while(!range.empty())
    {
        state = op(state, range.front());
        range.step_front();
    }
    return state;
}


template <typename State, class Range, typename BinaryOp>
State& fold_ref(Range range, State& state_ref, BinaryOp op)
{
    while(!range.empty())
    {
        op(state_ref, range.front());
        range.step_front();
    }
    return state_ref;
}



template <
    typename State,
    class Range,
    typename InitialOp,
    typename DefaultOp,
    typename FinalOp
> State& fold_ref(
    Range range,
    State& state_ref,
    InitialOp initial,
    DefaultOp op,
    FinalOp final
)
{
    if(!range.empty())
    {
        initial(state_ref, range.front());
        range.step_front();
        bool done = range.empty();
        while(!done)
        {
            auto front = range.front();
            range.step_front();
            done = range.empty();
            if(done)
            {
                final(state_ref, front);
                break;
            }
            else op(state_ref, front);
        }
    }
    return state_ref;
}

LAGOON_NAMESPACE_END

#endif //include guard