Arl: Embedded Lisp Dialect for R

Arl is a Scheme-inspired Lisp dialect embedded in R. It compiles Lisp source code to R expressions and evaluates them with R's own eval(), so all R functions and data structures are available directly with no foreign function interface. Arl provides a procedural macro system with automatic hygiene, self-tail-call optimization that rewrites recursive calls as loops, and a module system for organizing reusable code. The implementation is pure R with no compiled code. Arl is distributed as a standard R package and includes a REPL, a command-line interface, and a knitr language engine for literate programming.