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Add record type printer for srfi-41.

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* module/srfi/srfi-41.scm: Add record type printer for streams.
  (stream-promise-visit): New helper for visiting stream promises.
This commit is contained in:
Chris K. Jester-Young 2013-04-07 12:44:18 -04:00
parent 3ed8d953f8
commit b6e374e535
1 changed files with 23 additions and 0 deletions
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23
module/srfi/srfi-41.scm
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@ -27,6 +27,7 @@
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-8)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-9 gnu)
#:use-module (srfi srfi-26)
#:use-module (ice-9 match)
#:export (stream-null stream-cons stream? stream-null? stream-pair?
@ -180,6 +181,28 @@
(define-syntax-rule (stream-lambda formals body0 body1 ...)
(lambda formals (stream-lazy (begin body0 body1 ...))))
(define* (stream-promise-visit promise #:key on-eager on-lazy)
(define content (stream-promise-val promise))
(case (stream-value-tag content)
((eager) (on-eager (stream-value-proc content)))
((lazy) (on-lazy (stream-value-proc content)))))
(set-record-type-printer! stream-promise
(lambda (strm port)
(display "#<stream" port)
(let loop ((strm strm))
(stream-promise-visit strm
#:on-eager (lambda (pare)
(cond ((eq? pare %stream-null)
(write-char #\> port))
(else
(write-char #\space port)
(stream-promise-visit (stream-kar pare)
#:on-eager (cut write <> port)
#:on-lazy (lambda (_) (write-char #\? port)))
(loop (stream-kdr pare)))))
#:on-lazy (lambda (_) (display " ...>" port))))))
;;; Derived stream functions and macros: (streams derived)
(define-syntax-rule (define-stream (name . formal) body0 body1 ...)