chore: existential type
chore: existential type

rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming,rockdragon/julia-programming