Hello Damien! I am not sure I understand the reasoning behind condx: I think cond is already a macro, which only evaluates a consequent, if the predicate of its case is #t. Additionally multiple expressions are possible in each branch.
To clarify, I ask: What is the case, where condx does or does not evaluate some code, when cond would not or would? Or is it rather about the different nesting / sequence of expressions, which condx seems to enable? I think the flow you demonstrate might save a bit of nesting. Best regards, Zelphir On 9/11/21 11:14 AM, Damien Mattei wrote: > hello, > > i wrote a little macro (file condx.scm) that allow : cond(itionals) with > optional execution of statements before: > > (define-syntax condx > (syntax-rules (exec) > ((_) > (error 'condx "No else clause")) > ((_ (else e ...)) > (let () e ...)) > ((_ (exec s ...) d1 ...) > (let () s ... (condx d1 ...))) > ((_ (t e ...) tail ...) > (if t > (let () e ...) > (condx tail ...))))) > > use it like that: > > mattei@macbook-pro-touch-bar library-FunctProg % guile > GNU Guile 3.0.7 > Copyright (C) 1995-2021 Free Software Foundation, Inc. > > Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'. > This program is free software, and you are welcome to redistribute it > under certain conditions; type `,show c' for details. > > Enter `,help' for help. > scheme@(guile-user)> (load "condx.scm") > ;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0 > ;;; or pass the --no-auto-compile argument to disable. > ;;; compiling /Users/mattei/Dropbox/git/library-FunctProg/condx.scm > ;;; compiled > /Users/mattei/.cache/guile/ccache/3.0-LE-8-4.5/Users/mattei/Dropbox/git/library-FunctProg/condx.scm.go > scheme@(guile-user)> (define x 1) > > (condx ((= x 7) 'never) > (exec > (define y 3) > (set! x 7)) > ((= y 1) 'definitely_not) > (exec > (set! y 10) > (define z 2)) > ((= x 7) (+ x y z)) > (else 'you_should_not_be_here)) > $1 = 19 > > i share it to have idea about critics or idea to improve it as it will be > part of a Scheme extension to scheme language that will include other > features.... > > have a good day > > Damien -- repositories: https://notabug.org/ZelphirKaltstahl
