;; ** A language that is built as an extension on top of Racket

#lang racket

(provide (except-out (all-from-out racket)
                     let #%app #%module-begin))

(provide plus)
(define (plus x y) (+ x y))

(provide (rename-out [with let]))
(define-syntax-rule (with [x V] E)
                    (let ([x V]) E))

(provide (rename-out [my-app #%app]))
(define-syntax my-app
  (syntax-rules (=> @)
    [(_ x => E ...)
     (lambda x E ...)]
    [(_ F @ E ...)
     (list (F E) ...)]
    [(_ x ...) (x ...)]))

(provide (rename-out [mod-beg #%module-begin]))
(define-syntax-rule (mod-beg E ...)
                    (#%module-begin (verbose E) ...))
(define-syntax verbose
  (syntax-rules ()
    [(_ (define name value)) ; assume no (define (foo ...) ...)
     (begin (define name value)
            (printf "~s := ~s\n" 'name name))]
    [(_ E)
     (printf "~s --> ~s\n" 'E E)]))