Cool stuff. I think it's similar to custodians in Racket (the artist formerly known as PLT Scheme): http://docs.racket-lang.org/reference/eval-model.html#(part

Cool stuff. I think it's similar to custodians in Racket (the artist formerly known as PLT Scheme): http://docs.racket-lang.org/reference/eval-model.html#(part._custodian-model) http://docs.racket-lang.org/reference/eval-model.html#(part....