I extended DESTRUCTURING-BIND to allow NIL bindings to indicate a place should be ignored, the way that CL LOOP does. The fact that CL's DESTRUCTURING-BIND doesn't do that, but instead forces the user to make up a name and declare it ignored, is a perennial annoyance. Patch is below.
Daniel
From 5d8b60256a70788c0930724e9d3501551a5e1559 Mon Sep 17 00:00:00 2001
From: Daniel Gackle danielgackle@gmail.com Date: Fri, 8 May 2009 14:59:05 -0600 Subject: [PATCH 1/2] Extended DESTRUCTURING-BIND to allow NIL bindings to indicate a place should be ignored, the way that CL LOOP does.
--- src/lib/ps-macro-lib.lisp | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/src/lib/ps-macro-lib.lisp b/src/lib/ps-macro-lib.lisp index e6c32be..85a55ea 100644 --- a/src/lib/ps-macro-lib.lisp +++ b/src/lib/ps-macro-lib.lisp @@ -137,10 +137,13 @@ `((@ ,fn :apply) this ,arglist)))
(defpsmacro destructuring-bind (vars expr &body body) - ;; a simple implementation that for now only supports flat lists + ;; a simple implementation that for now only supports flat lists, + ;; but does allow NIL bindings to indicate ignore (a la LOOP) (let* ((arr (if (complex-js-expr? expr) (ps-gensym) expr)) (n -1) (bindings (append (unless (equal arr expr) `((,arr ,expr))) - (mapcar (lambda (var) `(,var (aref ,arr ,(incf n)))) vars)))) + (mapcan (lambda (var) + (incf n) + (when var `((,var (aref ,arr ,n))))) vars)))) `(let ,bindings ,@body)))