[parenscript-devel] Patch: destructuring-bind now supports dotted lists and nested lists

[Vladimir Sedach]

Just pushed this. Thanks for the patch!

On Fri, Jul 10, 2009 at 8:26 PM, Daniel Gackle<danielgackle at gmail.com> wrote:
> A couple of examples, followed by patch:
>
> (ps (destructuring-bind (a . rest) list
>           (blah a rest)))
> =>
> "var a = list[0];
> var rest = list.length > 1 ? list.slice(1) : null;
> blah(a, rest);"
>
> (ps (destructuring-bind ((a (b c)) (d e)) list))
> =>
> "var _js42 = list[0];
> var a = _js42[0];
> var _js43 = _js42[1];
> var b = _js43[0];
> var c = _js43[1];
> var _js44 = list[1];
> var d = _js44[0];
> var e = _js44[1];"
>
>
> From 74d29fe528d40795071e61df4fb1e4b56b28f049 Mon Sep 17 00:00:00 2001
> From: Daniel Gackle <danielgackle at gmail.com>
> Date: Fri, 10 Jul 2009 16:31:55 -0600
> Subject: [PATCH 1/2] DESTRUCTURING-BIND can now handle dotted and nested
> binding lists.
>
> ---
>  src/lib/ps-macro-lib.lisp |   31 +++++++++++++++++++++----------
>  1 files changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/src/lib/ps-macro-lib.lisp b/src/lib/ps-macro-lib.lisp
> index 1013939..d70561c 100644
> --- a/src/lib/ps-macro-lib.lisp
> +++ b/src/lib/ps-macro-lib.lisp
> @@ -144,14 +144,25 @@
>                       (first args))))
>      `((@ ,fn :apply) this ,arglist)))
>
> -(defpsmacro destructuring-bind (vars expr &body body)
> -  ;; a simple implementation that for now only supports flat lists,
> -  ;; but does allow NIL bindings to indicate ignore (a la LOOP)
> +(defun destructuring-wrap (arr n bindings body)
> +  (cond ((null bindings)
> +         body)
> +        ((atom bindings)
> +         ;; dotted destructuring list
> +         `(let ((,bindings (when (> (length ,arr) ,n)
> +                             ((@ ,arr :slice) ,n))))
> +            ,body))
> +        (t (let ((var (car bindings))
> +                 (inner-body (destructuring-wrap arr (1+ n) (cdr bindings)
> body)))
> +             (cond ((null var) inner-body)
> +                   ((atom var) `(let ((,var (aref ,arr ,n)))
> +                                  ,inner-body))
> +                   (t `(destructuring-bind ,var (aref ,arr ,n)
> +                         ,inner-body)))))))
> +
> +(defpsmacro destructuring-bind (bindings expr &body body)
>    (let* ((arr (if (complex-js-expr? expr) (ps-gensym) expr))
> -         (n -1)
> -         (bindings
> -          (append (unless (equal arr expr) `((,arr ,expr)))
> -                  (mapcan (lambda (var)
> -                            (incf n)
> -                            (when var `((,var (aref ,arr ,n))))) vars))))
> -    `(let* ,bindings , at body)))
> +         (bound (destructuring-wrap arr 0 bindings (cons 'progn body))))
> +    (if (eq arr expr)
> +        bound
> +        `(let ((,arr ,expr)) ,bound))))
> --
> 1.6.1
>
>
>
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