@noelle @mage ah, the parts about "no side effects" and "accepting user input" threw me off. determinism has to do with external causes and initial state, and is usually used to describe systems or algorithms or machines, not quite functions. for example "deterministic finite automata" refers to the class of state machines where there are n possible states and some way of moving consistently from any current state to adjacent states. https://en.wikipedia.org/wiki/Deterministic_finite_automaton