Hello,
Again, a question out of curiosity, because I think I found a solution, but
I'd like to have something more elegant.
I'm trying to use the (untyped) Racket generic graph library from my Typed
Racket code:
#lang typed/racket
(require/typed graph
[#:opaque Graph graph?]
[directed-graph (->* ((Listof (List Any Any))) ((Listof Any)) Graph)])
(directed-graph '((a b) (b c)))
When I load this code in the REPL I get
graph?: contract violation
any-wrap/c: Unable to protect opaque value passed as `Any`
value: #<unweighted-graph>
This warning will become an error in a future release.
in: the 1st argument of
a part of the or/c of
(or/c
struct-predicate-procedure?/c
(-> Any boolean?))
contract from: (interface for graph?)
blaming: <pkgs>/dds/tmp.rkt
(assuming the contract is correct)
at: <pkgs>/dds/tmp.rkt:4.18
#<unweighted-graph>
I found this solution by Alex Knauth:
https://stackoverflow.com/questions/65386334/racket-generic-graph-library-in-typed-racket
, which essentially consists in wrapping the opaque graph struct into
another struct. Alex says that the problem comes from the fact that graph?
essentially encompasses a couple different internal representations the
graph library uses.
While this solution should fit me, I was wondering whether anybody here has
encountered this issue and has a different solution.
-
Sergiu
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