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

17 lines
588 B
Racket

#lang br
(require "struct.rkt")
(provide (all-defined-out))
(define-macro (b-line NUM STATEMENT ...)
(with-pattern ([LINE-NUM (prefix-id "line-" #'NUM
#:source #'NUM)])
(syntax/loc caller-stx
(define (LINE-NUM #:error [msg #f])
(with-handlers ([line-error? (λ (le) (handle-line-error NUM le))])
(when msg (raise-line-error msg))
STATEMENT ...)))))
(define (handle-line-error num le)
(error (format "error in line ~a: ~a" num (line-error-msg le))))
(define (raise-line-error str) (raise (line-error str)))