I'm trying to make sense of how prefix/rename work for signatures, but in
trying to run some examples the actual implementation doesn't seem to match
either my intuition or the documentation.
For example I have the following simple signature:
(define-signature a^ (a))
I then try to build a new signature from a^ with a combination of open and
prefix/rename.
(define-signature b-bad^
((open (prefix x: (rename (prefix y: a^) (q y:a))))))
This example, however, gives the error:
"open: listed identifier not present in signature specification in: x:y:a"
I'm not sure I understand this since it appears as though prefixing x: comes
before the renaming, but I would have though that first y: is prefixed to a, so
that y:a is in the signature which can then be renamed q. So in the end the
only variable in the signature should be x:q.
Attempting the same in a unit form gives a similar error:
(define u-bad
(unit (import (prefix x: (rename (prefix y: a^) (q y:a))))
(export)
x:q))
"unit: listed identifier not present in signature specification in: x:y:a"
If I change the prefix x: to y: things seem to work for some reason.
(define-signature b-good^
((open (prefix y: (rename (prefix y: a^) (q y:a))))))
In this case, I still expect the variable in the signature to be something like
y:q, but trying a similar renaming in a unit form fails:
(define u-bad2
(unit (import (prefix y: (rename (prefix y: a^) (q y:a))))
(export)
y:q))
With the error:
"y:q: unbound identifier in module in: y:q"
while the following does work
(define u-good
(unit (import (prefix y: (rename (prefix y: a^) (q y:a))))
(export)
q))
Am I misunderstanding something obvious about the way that the
renaming/prefixing should be taking place on the level of a signature or unit
import/export clause? The results I'm seeing are completely unintuitive to me
and the documentation doesn't seem to clarify this for me.
Thanks
Dan
____________________
Racket Users list:
http://lists.racket-lang.org/users
