qretty is a Ruby library that makes it possible to dynamically derive, based on an annotated grammar of a language, an object-oriented API for building models representing expressions in the language. qretty also produces code for pretty printing the models according to hints in the grammar. This work was done in Services for All (E!2023 ITEA S4ALL).
To use qretty, you must unpack both qretty and codeprint distributions somewhere, and then have your RUBYLIB environment variable point to both the qretty and codeprint lib directories. codeprint is a library in which qretty depends on for low-level text formatting tasks.