sort_cache_by.jl

sort_cache_by.jl

import Base: getindex, setindex, length, isless

struct SortPair{A,B}
    x::A
    mapped::B
end

struct SortCache{A,B,AV,BV} <: AbstractVector{SortPair{A,B}}
    xs::AV
    mapped::BV

    function SortCache(xs::AbstractVector{T}, f) where T
        mapped = map(f, xs)
        new{T,eltype(mapped),typeof(xs),typeof(mapped)}(xs, mapped)
    end
end

Base.size(xs::SortCache) = size(xs.xs)

Base.@propagate_inbounds function Base.getindex(xs::SortCache, i::Int) 
    return SortPair(xs.xs[i], xs.mapped[i])
end

Base.@propagate_inbounds function Base.setindex!(xs::SortCache, v::SortPair, i::Int)
    xs.xs[i] = v.x
    xs.mapped[i] = v.mapped
    return v
end

Base.isless(lhs::SortPair, rhs::SortPair) = isless(lhs.mapped, rhs.mapped)

function sort_with_cached_by(xs; by = identity)
    sort!(SortCache(xs, by))
    return xs
end

z_example.jl

sort_with_cached_by(rand(Int, 100), by = abs)