Hi Dan, I'm afraid you can't. If you want to write unions of polymorphic variant types, they have to be concrete and not abstract. See Romain Bardou's work on this:
http://romain.bardou.fr/papers/stage2006p.pdf Or, if you can read french: www.math.nagoya-u.ac.jp/~garrigue/papers/index.html (see Unions de variants polymorphes abstraits). Cheers, Philippe. 2012/5/7 Dan Bensen <danben...@att.net> > > I'm trying to write a functor that extends a user-supplied polymorphic > variant type (PVT). How do you declare the user's type in the signature > for the argument to the functor without locking in the individual variant > definitions? > The code below (in revised syntax) generates an error message that says > the type isn't a PVT. > > code: > > > module type Reader = sig type ast; end; > > > > module Make (Read: Reader) = struct > > type ast = [= Read.ast | `Lid of string]; > > end; > > message: > > > Error: The type Read.ast is not a polymorphic variant type > > How do you make ast a PVT while allowing the user to > specify the variants? > -- Caml-list mailing list. Subscription management and archives: https://sympa-roc.inria.fr/wws/info/caml-list Beginner's list: http://groups.yahoo.com/group/ocaml_beginners Bug reports: http://caml.inria.fr/bin/caml-bugs
