s-expressions can provide a hierarchical structure, but they are not representing AST. It's just another form of source code. > And, of course, an interpreter

s-expressions can provide a hierarchical structure, but they are not representing AST. It's just another form of source code. > And, of course, an interpreter that works by walking S-Expressions is really, really slow. Common Lisp interpreters work by walking S-expressions. Typically you'll see the s-expressions directly in a debugger -> modifying the s-expression will modify the running program.