> If a language has only immutable data structures, it is easy to make it so that self-reference becomes impossible, just by making sure your primitives for con

> If a language has only immutable data structures, it is easy to make it so that self-reference becomes impossible, just by making sure your primitives for constructing values don't permit cycles to be constructed. Much like the Y combinator comes out somewhat unexpectedly from the pure lambda calculus, my suspicion is that any sufficiently rich data-construction language will allow, intentionally or unintentionally, for some sort of self-reference.