They are written on top, but not in. It's like claiming Ruby programs are written in characters. S-expressions know nothing and represent nothing about concept

They are written on top, but not in. It's like claiming Ruby programs are written in characters. S-expressions know nothing and represent nothing about concepts like functions, variables, argument lists, operators, bindings, type declarations, function defintions, variable defintions, class definitions, ... Even syntactic (3 4 +) is READ successfully, but it is not a valid Clojure form. Basically a READER is on the level of a TOKENIZER, but not a parser.