On 14 Oct 2009, at 9:37 am, Ray Dillinger wrote:
> I think lambda's not quite right because it provides only nested
> scopes.
>
> Firstly there's a nesting depth beyond which I'm uncomfortable.
>
> Secondly there's sometimes a need for a scope visible in places
> separated by other places where it's not visible.
Oh, you can do all that stuff (apart from macros, as they're not
values, but there's ways to deal with that) - you can treat a 'module'
as a closure that accepts a closure and applies it to the contents of
the module... like this:
(define my-silly-addition-module
(lambda (body)
(body
(lambda (a b) (+ a b 1)) ; here we define everything our module
exports
)))
Clearly, we can have some private internal bindings in the module, by
wrapping the outer lambda in a let.
....then to use the module, we apply it...
(my-silly-addition-module
(lambda (silly-add) ; declare your imports here
(silly-add 1 2)))
The user of the module needs to explicitly declare all the symbols
they want (and even the ones they don't!), but these lambda-modules
give you full arbitrary renaming capability on import :-)
--
Alaric Snell-Pym
Work: http://www.snell-systems.co.uk/
Play: http://www.snell-pym.org.uk/alaric/
Blog: http://www.snell-pym.org.uk/archives/author/alaric/
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