New upstream version 3b5upstream/3b5upstream

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+; "fluidlet.scm", FLUID-LET for Scheme
+; Copyright (c) 1998, Radey Shouman <radey_shouman@splashtech.com>
+;
+;Permission to copy this software, to redistribute it, and to use it
+;for any purpose is granted, subject to the following restrictions and
+;understandings.
+;
+;1.  Any copy made of this software must include this copyright notice
+;in full.
+;
+;2.  I have made no warrantee or representation that the operation of
+;this software will be error-free, and I am under no obligation to
+;provide any services, by way of maintenance, update, or otherwise.
+;
+;3.  In conjunction with products arising from the use of this
+;material, there shall be no use of my name in any advertising,
+;promotional, or sales literature without prior written consent in
+;each case.
+
+(require 'dynamic-wind)
+(require 'macro)
+
+(define-syntax fluid-let
+  (syntax-rules ()
+    ((_ ((?name ?val) ...) . ?body)
+     (fluid-let "make-temps"
+       ((?name ?val) ...) () ()
+       ((?name ?val) ...) . ?body))
+    ((_ "make-temps" (?bind1 . ?binds) ?olds ?news . ?rest)
+     (fluid-let "make-temps"
+       ?binds
+       (old-tmp . ?olds)
+       (new-tmp . ?news) . ?rest))
+    ((_ "make-temps" () (?old ...) (?new ...) ((?name ?val) ...) . ?body)
+     (let ((?new ?val) ... (?old #f) ...)
+       (dynamic-wind
+	(lambda () (set! ?old ?name) ... (set! ?name ?new) ...)
+	(lambda () . ?body)
+	(lambda () (set! ?new ?name) ... (set! ?name ?old) ...))))))