mutable struct PreVector{T}
    last_ind::UInt64
    v::Vector{T}

    PreVector(T, N) = new{T}(UInt64(0), Vector{T}(undef, N))
end

function push!(pv::PreVector{T}, x::T) where {T}
    pv.last_ind += 1
    pv.v[pv.last_ind] = x

    return nothing
end

function reset!(pv::PreVector{T}) where {T}
    pv.last_ind = 0

    return nothing
end