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-rw-r--r--module/rnrs/io/ports.scm18
1 files changed, 13 insertions, 5 deletions
diff --git a/module/rnrs/io/ports.scm b/module/rnrs/io/ports.scm
index 594606785..c19aee9af 100644
--- a/module/rnrs/io/ports.scm
+++ b/module/rnrs/io/ports.scm
@@ -1,6 +1,6 @@
;;;; ports.scm --- R6RS port API -*- coding: utf-8 -*-
-;;;; Copyright (C) 2009, 2010, 2011, 2013 Free Software Foundation, Inc.
+;;;; Copyright (C) 2009-2011, 2013, 2019 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
@@ -269,13 +269,21 @@ if the port has no transcoder."
"unsupported error handling mode"))))))
(define (binary-port? port)
- "Always returns @code{#t}, as all ports can be used for binary I/O in
-Guile."
+ "Return @code{#t} if @var{port} appears to be a binary port, else
+return @code{#f}. Note that Guile does not currently distinguish
+between binary and textual ports, so this predicate is not a reliable
+indicator of whether the port was created as a binary port. Currently,
+it returns @code{#t} if and only if the port encoding is ``ISO-8859-1'',
+because Guile uses this encoding when creating a binary port."
(equal? (port-encoding port) "ISO-8859-1"))
(define (textual-port? port)
- "Always returns @code{#t}, as all ports can be used for textual I/O in
-Guile."
+ "Return @code{#t} if @var{port} appears to be a textual port, else
+return @code{#f}. Note that Guile does not currently distinguish
+between binary and textual ports, so this predicate is not a reliable
+indicator of whether the port was created as a textual port. Currently,
+it always returns @code{#t}, because all ports can be used for textual
+I/O in Guile."
#t)
(define (port-eof? port)