Tree calculus: a Turing-complete language where programs are just trees

Tree calculus is a minimal, modular, Turing-complete and reflective calculus where programs and values are unlabeled binary trees. This visual introduction explains the reduction rules of triage calculus, shows how to represent data like booleans and lists, and demonstrates constructing programs such as 'not' and 'size'. The author tested the explanation on his mom, who had no prior knowledge of lambda calculus, and she successfully reduced expressions with pen and paper.