From 97cc883b966c779885c7cd52fabb8801443b3031 Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Mon, 18 Aug 2008 06:40:18 +0000
Subject: [PATCH] in PROVIDE-INPUT-FEATURES, don't advertise operations that
 aren't supported.

---
 v7/src/runtime/port.scm | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/v7/src/runtime/port.scm b/v7/src/runtime/port.scm
index d6ed67c12..168d64654 100644
--- a/v7/src/runtime/port.scm
+++ b/v7/src/runtime/port.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: port.scm,v 1.58 2008/07/26 05:12:20 cph Exp $
+$Id: port.scm,v 1.59 2008/08/18 06:40:18 cph Exp $
 
 Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
     1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
@@ -290,16 +290,18 @@ USA.
 	       char))))
 	(unread-char
 	 (let ((defer (op 'UNREAD-CHAR)))
-	   (lambda (port char)
-	     (defer port char)
-	     (set-port/unread?! port #t))))
+	   (and defer
+		(lambda (port char)
+		  (defer port char)
+		  (set-port/unread?! port #t)))))
 	(peek-char
 	 (let ((defer (op 'PEEK-CHAR)))
-	   (lambda (port)
-	     (let ((char (defer port)))
-	       (transcribe-input-char char port)
-	       (set-port/unread?! port #t)
-	       char))))
+	   (and defer
+		(lambda (port)
+		  (let ((char (defer port)))
+		    (transcribe-input-char char port)
+		    (set-port/unread?! port #t)
+		    char)))))
 	(read-substring
 	 (let ((defer (op 'READ-SUBSTRING)))
 	   (lambda (port string start end)
-- 
2.25.1