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Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...)))
From: |
Stefan Monnier |
Subject: |
Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))) |
Date: |
Sun, 02 Jan 2011 21:19:44 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux) |
> In Scheme, the expression:
> (cond (EXPR => (lambda (X) ...)))
> provides the lambda expression parameter X with the non-false
> value computed from evaluating EXPR. However, if EXPR evaluates
> to false, control falls through to the next ‘cond’ clause, as
> usual. The syntax requires the symbol ‘=>’ between EXPR and the
> lambda expression, without which the non-false value is discarded
> (i.e., the status quo).
> What do people think of adding this to Emacs Lisp? (I would be
> grateful for pointers to any previous discussion on the matter.)
Doesn't sound bad: it's a conservative extension which doesn't seem to
introduce any significant incompatibility. The only problem I can see
with it is that it relies on a function call, which is a slow operation
in the current Elisp implementation.
Stefan
- emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))), Thien-Thi Nguyen, 2011/01/02
- Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))),
Stefan Monnier <=
- Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))), Richard Stallman, 2011/01/03
- Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))), Stefan Monnier, 2011/01/05
- Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))), Harald Hanche-Olsen, 2011/01/05
- Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))), Stefan Monnier, 2011/01/05