Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...)))

[Stefan Monnier <monnier@iro.umontreal.ca>]

> 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