picrin/contrib/20.repl/repl.scm

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(define-library (picrin repl)
(import (scheme base)
(scheme read)
(scheme write)
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(scheme eval))
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(cond-expand
((library (picrin readline))
(import (picrin readline)
(picrin readline history)))
(else
(begin
(define (readline str)
(display str)
(read-line))
(define (add-history str)
#f))))
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(define (repl)
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(let loop ((buf ""))
(let ((line (readline (if (equal? buf "") "> " "* "))))
(if (eof-object? line)
(newline) ; exit
(let ((str (string-append buf line "\n")))
(add-history line)
(call/cc
(lambda (exit)
(with-exception-handler
(lambda (condition)
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(if (error-object? condition)
(unless (equal? (error-object-message condition) "unexpected EOF")
(display "error: ")
(display (error-object-message condition))
(newline)
(set! str ""))
(begin
(display "raised: ")
(write condition)
(newline)
(set! str "")))
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(exit))
(lambda ()
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(call-with-port (open-input-string str)
(lambda (port)
(let next ((expr (read port)))
(unless (eof-object? expr)
(write (eval expr '(picrin user)))
(newline)
(set! str "")
(next (read port))))))))))
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(loop str))))))
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(export repl))
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