[plt-scheme] multiple units with identical signatures

Anthony Cowley wrote:
> (define-compound-unit together@
>   (import)
>   (export T)
>   (link (((P : page^)) page@)
>         (((I : info^)) info@)
>         (((T : top^)) top@ P I)))

Woah! You know how to do that associative symbol unit linking thingy?
That's not even correct in the docs! Okay I think I can work with that,
thanks.