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beautiful-racket/beautiful-racket-demo/basic-demo/expander.rkt

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Racket

#lang br/quicklang
(define-macro (b-module-begin (b-program LINE ...))
(with-pattern ([(LINE-NUM ...)
(filter-stx-prop 'b-line-number (syntax-flatten #'(LINE ...)))]
[(LINE-ID ...) (syntax-map (λ (stx) (prefix-id "line-" stx)) #'(LINE-NUM ...))])
#'(#%module-begin
LINE ...
(define line-table (apply hasheqv (append (list LINE-NUM LINE-ID) ...)))
(run line-table))))
(provide (rename-out [b-module-begin #%module-begin]))
(define-macro (b-line LINE-NUMBER STATEMENT)
(with-pattern ([LINE-NUMBER-ID (prefix-id "line-" #'LINE-NUMBER
#:source #'LINE-NUMBER)]
[ORIG-LOC caller-stx])
(syntax/loc caller-stx (define (LINE-NUMBER-ID #:srcloc? [srcloc #f])
(if srcloc
(syntax-srcloc #'ORIG-LOC)
STATEMENT)))))
(define (b-statement stmt) stmt)
(define (b-rem str) #f)
(define (b-print str) (displayln str))
(define (b-goto line-number) line-number)
(define-exn end-program-signal exn:fail)
(define (b-end) (raise-end-program-signal))
(provide b-line b-statement b-rem b-print b-goto b-end)
(define-exn-srcloc line-not-found exn:fail)
(define (run line-table)
(define line-vec (list->vector (sort (hash-keys line-table) <)))
(with-handlers ([end-program-signal? void])
(for/fold ([line-idx 0])
([i (in-naturals)])
(unless (< line-idx (vector-length line-vec)) (b-end))
(define line-num (vector-ref line-vec line-idx))
(define line-proc (hash-ref line-table line-num))
(define line-result (line-proc))
(if (exact-positive-integer? line-result)
(or (vector-member line-result line-vec)
(raise-line-not-found (line-proc #:srcloc? #t)))
(add1 line-idx)))))