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Diffstat (limited to 'fluidlet.scm')
-rw-r--r-- | fluidlet.scm | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/fluidlet.scm b/fluidlet.scm new file mode 100644 index 0000000..c93b288 --- /dev/null +++ b/fluidlet.scm @@ -0,0 +1,45 @@ +; "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 |