This article covers setting up Common Lisp with GADTs and exhaustive pattern-matching checks. https://chriskohlhepp.wordpress.com/metacircular-adventures-in-fun

This article covers setting up Common Lisp with GADTs and exhaustive pattern-matching checks. https://chriskohlhepp.wordpress.com/metacircular-adventures-in-functional-abstraction-challenging-clojure-in-common-lisp/ https://chriskohlhepp.wordpress.com/metacircular-adventures-... > We note that we get a non-exhaustive match warning at compile time, not run time. This is the behaviour we would expect for example from OCaml. Indeed, in our little game we might change the simple use of keyword symbols to algebraic data types and thus add compiler hosted verification of our pattern matches. To bring our exploration of the meta-circular abstraction to a full circle: Abstract data-types are an ideal medium in which to represent Abstract Syntax Trees or ASTs. Indeed the whole of Lisp syntax is itself fundamentally an Abstract Syntax Tree. So let’s see if we can represent trees using the cl-algebraic-datatype package. That would amount to an Abstract Syntax Tree represented inside an Abstract Syntax Tree. We will close with that that little teaser.