I really like de Bruijn indexes, but whenever alternatives are suggested I always like to mention the paper "I am not a number, I am a free variable", if only f

I really like de Bruijn indexes, but whenever alternatives are suggested I always like to mention the paper "I am not a number, I am a free variable", if only for the title ;) https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.365.2479&rep=rep1&type=pdf https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.36...