73 lines
2.3 KiB
Scheme
73 lines
2.3 KiB
Scheme
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(let ()
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(define with-error-handler
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(lambda (p thunk)
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(let ([old-error-handler (current-error-handler)])
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(dynamic-wind
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(lambda ()
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(current-error-handler
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(lambda args
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(current-error-handler old-error-handler)
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(apply p args)
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(apply error args))))
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thunk
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(lambda ()
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(current-error-handler old-error-handler))))))
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(define eval-depth 0)
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(define display-prompt
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(lambda (i)
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(if (fx= i eval-depth)
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(display " " (console-output-port))
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(begin
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(display ">" (console-output-port))
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(display-prompt (fx+ i 1))))))
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(define wait
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(lambda (eval escape-k)
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(call/cc
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(lambda (k)
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(with-error-handler
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(lambda args
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(reset-input-port! (console-input-port))
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(apply print-error args)
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(k (void)))
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(lambda ()
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(display-prompt 0)
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(let ([x (read (console-input-port))])
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(cond
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[(eof-object? x)
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(newline (console-output-port))
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(escape-k (void))]
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[else
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(call-with-values
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(lambda () (eval x))
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(lambda v*
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(unless (andmap (lambda (v) (eq? v (void))) v*)
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(for-each
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(lambda (v)
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(write v (console-output-port))
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(newline (console-output-port)))
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v*))))]))))))
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(wait eval escape-k)))
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($pcb-set! new-cafe
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(lambda args
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(let ([eval
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(if (null? args)
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(current-eval)
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(if (null? (cdr args))
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(let ([f (car args)])
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(if (procedure? f)
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f
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(error 'new-cafe "not a procedure ~s" f)))
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(error 'new-cafe "too many arguments")))])
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(dynamic-wind
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(lambda () (set! eval-depth (fxadd1 eval-depth)))
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(lambda ()
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(call/cc
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(lambda (k)
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(wait eval k))))
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(lambda () (set! eval-depth (fxsub1 eval-depth))))))))
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