Cheney's algorithm is an improvement on the semi-space collector.

Cheney's algorithm reclaims items as follows:

Currently, Idris compiles to C and relies on a custom copying garbage collector using Cheney's algorithm.

Cheney's algorithm, first described in a 1970 ACM paper by C.J. Cheney, is a method of garbage collection in computer software systems.

The computer scientist Henry Baker references the song in his paper CONS Should Not CONS Its Arguments, Part II: Cheney on the M.T.A., which describes a way of implementing Cheney's algorithm using C functions that, like Charlie, never return.