Re: keywords in 1.2

[Maciej Stachowiak <mstachow@mit.edu>]

craig@onshore.com writes:
> 
> I am writing a little makefile generator for the various documentation
> tools we use around the office here, and I wanted to use keywords to
> do a little deffin' and was surprised to find keywords apparently
> busticated in guile 1.2.   I have not tried any other version so far.
> 
> For example:
> 
> guile> (keyword? :key)
> ERROR: While evaluating arguments to keyword? in expression (keyword? :key):
> ERROR: Unbound variable: :key
> ABORT: (misc-error)
> 
> Should it not just evaluate to itself?  This is straight from an
> example in the docs.  This works in CMUCL 8^)
> 
> Please tell me I'm doing something wrong.  I can work around this by
> just making some symbols, but keywords are just so darn useful for
> this.

You can either use #:keyword as the syntax (this is the default print
and read syntax) or you can use a reader option to also recognize the
:keyword syntax, but I forget what it is (I thought is was
(read-enable 'keywords) but that doesn't work for me).

I reccomend using the #:keyword syntax, as apparently there is useful
Scheme library code out there that has symbols starting with a
colon. Incidentally, if you want to have nice handling of keyword
arguments (and optional args as well), you can try the file
scheme/optargs.scm in the scwm distribution. An improved version of
this will likely make its way into Guile as soon as I can get papers
signed by my company (I hate lawyers); it provides lambda*, define*,
define*-public etc which take lambda-lists rather similar to Common
Lisp. Extensive docs are in the file. If you are planning to use
keywords for purposes other than keyword arguments, I reccomend
against; quoted symbols are generally better for such pruposes.

 - Maciej