Hi Richard,
On Wed 27 Feb 2013 15:22, Richard Shann <richard.sh...@virgin.net> writes:
> On Wed, 2013-02-27 at 08:19 -0500, m...@markwitmer.com wrote:
>> Richard Shann <richard.sh...@virgin.net> writes:
>>
>> > (if (not (defined? 'ToggleTripleting::InsideTriplet))
>> > (define ToggleTripleting::InsideTriplet #t))
I'm sorry we were not able to make this case work in Guile 2; it's quite
complicated actually.
>> You can probably just replace your code with
>>
>> (define-once ToggleTripleting::InsideTriplet #t)
>
> Thanks for this - it seems define-once is not defined in guile 1.8
> however
You could define it in a prelude somewhere:
(cond-expand
(guile-2) ; nothing
(else ; guile < 2.0
(define-macro (define-once sym exp)
`(if (not (defined? ',sym)) (define ,sym ,exp)))))
Then you could change all uses of this idiom to use define-once.
Note that Guile 2.'s `define-once' is slightly different; it always
declares a local definition, and it uses the existing value only if
there is already a local definition. In this way imported values get
overridden by define-once.
Here is a Guile 2-compatible version:
(cond-expand
(guile-2) ; nothing
(else ; guile < 2.0
(define-macro (define-once sym exp)
`(define ,sym (if (module-locally-bound? ',sym) ,sym ,val)))))
Finally in Guile 2 there is also the `define!' procedure, which makes
top-level definitions programmatically. Use it if you need it. But if
you can, better to rewrite to use standard Scheme.
In general I recommend adding shims to Denemo to make it
forward-compatible -- like adding define-once if needed so that it uses
the Guile 2.0 idioms, even on 1.8.
Good luck, and let us know how it goes.
Andy
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