From: Chris Hanson <org/chris-hanson/cph>
Date: Wed, 13 Mar 2002 05:47:01 +0000 (+0000)
Subject: Add definitions for LINK-VARIABLES and UNBIND-VARIABLE.
X-Git-Tag: 20090517-FFI~2200
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=c79c2dab8dfd2e7e5ffb90137bad9a2c720b1cb3;p=mit-scheme.git

Add definitions for LINK-VARIABLES and UNBIND-VARIABLE.
---

diff --git a/v7/doc/ref-manual/scheme.texinfo b/v7/doc/ref-manual/scheme.texinfo
index 6210db8c9..a614207d0 100644
--- a/v7/doc/ref-manual/scheme.texinfo
+++ b/v7/doc/ref-manual/scheme.texinfo
@@ -2,7 +2,7 @@
 @iftex
 @finalout
 @end iftex
-@comment $Id: scheme.texinfo,v 1.115 2002/03/01 03:23:23 cph Exp $
+@comment $Id: scheme.texinfo,v 1.116 2002/03/13 05:47:01 cph Exp $
 @comment %**start of header (This is for running Texinfo on a region.)
 @setfilename scheme.info
 @settitle MIT Scheme Reference
@@ -51,7 +51,7 @@ Free Documentation License".
 @title{MIT Scheme Reference Manual}
 @subtitle Edition 1.96
 @subtitle for Scheme Release 7.7.0
-@subtitle 28 February 2002
+@subtitle 13 March 2002
 @author by Chris Hanson
 @author the MIT Scheme Team
 @author and a cast of thousands
@@ -13357,6 +13357,28 @@ If neither @var{names} nor @var{values} is specified, the environment
 will have no initial bindings.
 @end deffn
 
+@deffn procedure link-variables environment1 symbol1 environment2 symbol2
+Defines @var{symbol1} in @var{environment1} to have the same binding as
+@var{symbol2} in @var{environment2}, and returns an unspecified value.
+Prior to the call, @var{symbol2} must be bound in @var{environment2},
+but the type of binding is irrelevant; it may be a normal binding, an
+unassigned binding, or a keyword binding.  Signals an error if
+@var{symbol1} isn't definable in @var{environment1}, or if @var{symbol2}
+is unbound in @var{environment2}.
+
+By ``the same binding'', we mean that the value cell is shared between
+the two environments.  If a value is assigned to @var{symbol1} in
+@var{environment1}, a subsequent reference to @var{symbol2} in
+@var{environment2} will see that value, and vice versa.
+@end deffn
+
+@deffn procedure unbind-variable environment symbol
+If @var{symbol} is bound in @var{environment} or one of its ancestor
+environments, removes the binding, so that subsequent accesses to that
+symbol behave as if the binding never existed.  Returns @code{#t} if there
+was a binding prior to the call, and @code{#f} if there wasn't.
+@end deffn
+
 @node Input/Output, Operating-System Interface, Environments, Top
 @chapter Input/Output