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beautiful-racket/beautiful-racket-demo/basic-demo-2/expr.rkt

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Racket

#lang br
(provide b-expr b-sum b-product b-neg b-expt)
(define (b-expr expr)
(if (integer? expr) (inexact->exact expr) expr))
(define-macro-cases b-sum
[(_ VAL) #'VAL]
[(_ LEFT "+" RIGHT) #'(+ LEFT RIGHT)]
[(_ LEFT "-" RIGHT) #'(- LEFT RIGHT)])
(define-macro-cases b-product
[(_ VAL) #'VAL]
[(_ LEFT "*" RIGHT) #'(* LEFT RIGHT)]
[(_ LEFT "/" RIGHT) #'(/ LEFT RIGHT 1.0)]
[(_ LEFT "mod" RIGHT) #'(modulo LEFT RIGHT)])
(define-macro-cases b-neg
[(_ VAL) #'VAL]
[(_ "-" VAL) #'(- VAL)])
(define-macro-cases b-expt
[(_ VAL) #'VAL]
[(_ LEFT "^" RIGHT) #'(expt LEFT RIGHT)])