[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: New draft



Marc Feeley <feeley@iro.umontreal.ca> writes:

> The new syntax does away with the `#!optional', `#!key' and `#!rest'
> markers.  Instead, a syntax that is inspired from EBNF is used to
> denote optional parts (square brackets in the parameter list around
> the optional parameters).

Considering that R6RS will standardize brackets as being
equivalent to parentheses[1], this SRFI will also allow

  (define (myproc required (optional #f) (key: key #t))
    ...)

I assume this is intended, and I want to state that I like this
syntax, and I definitively prefer it very much over the old.

It /might/ be preferable to some people if this SRFI would specify
LAMBDA-KW and DEFINE-KW special forms (the names up for debate of
course) instead of shadowing R5RS’ forms. A useful module system
can be used to explicitly shadow the R5RS forms if someone
requires the extended capabilities in LAMBDA and DEFINE itself.


This SRFI allows the following function definition:

  (define (foo (bar: bar 2) (baz 3))
    ...)

But for this procedure, it would disallow the analogical
invocation:

  (foo bar: 5 'baz-value)

In this example, BAZ is bound to the keyword BAR:, and the
application then is invalid due to too many arguments. To make
this dependence on order explicit, I think it would be useful to
only allow optional arguments to be specified before keyword
arguments.


Regards,
        -- Jorgen

[1] The March 2005 R6RS Status Report
    http://www.schemers.org/Documents/Standards/Charter/mar-2005.txt

-- 
((email . "forcer@forcix.cx") (www . "http://www.forcix.cx/";)
 (gpg   . "1024D/028AF63C")   (irc . "nick forcer on IRCnet"))