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+; "fluidlet.scm", FLUID-LET for Scheme
+; Copyright (c) 1992, Dorai Sitaram (dorai@cs.rice.edu)
+;
+;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 'rev4-optional-procedures)
+(require 'common-list-functions)
+(require 'dynamic-wind)
+(require 'macro)
+
+(define list-set! (lambda (s i v) (set-car! (list-tail s i) v)))
+
+(define-syntax fluid-let
+  (syntax-rules ()
+    ((fluid-let ((x v) ...) . body)
+     (let ((%x-names (list 'x ...))
+	   (%x-values (list x ...))
+	   (%fluid-x-values (list v ...)))
+       (dynamic-wind
+	 (lambda ()
+           (set! x (list-ref %fluid-x-values
+		       (comlist:position 'x %x-names)))
+           ...)
+	 (lambda () . body)
+	 (lambda ()
+           (let ((%x-position (comlist:position 'x %x-names)))
+             (list-set! %fluid-x-values %x-position x)
+	     (set! x (list-ref %x-values %x-position)))
+	   ...))))))
+
+;--- end of file