small-cl-src-discuss

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September 2004

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[Small-cl-src-discuss] Re: [Small-cl-src] What would var+++ be in CL?
by Douglas Philips 29 Sep '04

29 Sep '04

On Sep 23, 2004, at 11:05 AM, Ingvar wrote: > ;;; Possibly a tad naive, but... > (defmacro post-incf (form &optional (increment 1)) > (let ((value (gensym "POST-INCF"))) > `(let ((,value ,form)) > (prog1 ,value (setf ,form (+ ,value ,increment)))))) Actually, this came up on comp.lang.lisp and a few good versions were posted there. i'm accessing the net via a temp. connection (i'm on vacation), else I'd just search and give the pointer to the posts myself. <D\'gou

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[Small-cl-src-discuss] Re: [Small-cl-src] with-carry
by marco 29 Sep '04

29 Sep '04

Peter Lewerin <peter.lewerin(a)swipnet.se> writes: > #| > In a reply to me in c.l.l., Adam Warner suggested a control structure for the > cases when a computation is made in stages, with the result of each stage used > somewhere in the next stage. The following is basically his code; I added a > SYMBOL-MACROLET wrapper to be able to name the carry-over variable. > > See c.l.l. thread "Which style do you prefer?" > |# > > (defmacro with-carry (c stages &body body) > (symbol-macrolet ((_ c)) > `(let* (,@(loop for item in stages collect (list _ item))) > ,@body))) > > ;; (with-carry x ((+ 2 3) (* x 10)) (print x)) > ;; => 50 > ;; expands to: (LET* ((X (+ 2 3)) (X (* X 10))) (PRINT X)) this reminded me of: http://groups.google.com/groups?selm=ahnk8t%247d5%241%40luna.vcn.bc.ca -- -Marco Ring the bells that still can ring. Forget your perfect offering. There is a crack in everything. That's how the light gets in. -Leonard Cohen

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