37 lines
1.2 KiB
Racket
37 lines
1.2 KiB
Racket
#lang racket/base
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(provide fresh-line
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zero-column!)
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;; Borrowed from xrepl
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(define last-output-port #f)
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(define last-error-port #f)
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(define (maybe-new-output-ports)
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(define-syntax-rule (maybe last cur)
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(unless (eq? last cur)
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(when (and last
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(not (port-closed? last)))
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(flush-output last)) ;just in case
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(set! last cur)
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(flush-output last)
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(port-count-lines! last)))
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(maybe last-output-port (current-output-port))
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(maybe last-error-port (current-error-port)))
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(define (fresh-line [stderr? #f])
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(maybe-new-output-ports)
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(define port (if stderr? last-error-port last-output-port))
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(flush-output port)
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(define-values [line col pos] (port-next-location port))
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(unless (eq? col 0) (newline)))
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(define (zero-column!)
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;; there's a problem whenever there's some printout followed by a
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;; read: the cursor will be at column zero, but the port counting
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;; will think that it's still right after the printout; call this
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;; function in such cases to adjust the column to 0.
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(maybe-new-output-ports)
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(define-values [line col pos] (port-next-location last-output-port))
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(set-port-next-location! last-output-port line 0 pos))
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