This is a consequence of value restriction, with a direct workaround. See the FAQ:
"A function obtained through partial application is not polymorphic enough" http://caml.inria.fr/resources/doc/faq/core.en.html#eta-expansion let get1 a b = let must x = lmust "get2" x in .... On Fri, Mar 23, 2012 at 5:58 AM, David Brown <c...@davidb.org> wrote: > I'm trying to figure out how to get 'lmust' in 'get2' in the code > below to work. It seems that it's type is being inferred as > > string -> string option -> string > > instead of > > string -> 'a option -> 'a > > The 'must' definition keeps it's polymorphism, as seen in 'get1'. Is > there some way I can annotate the definition of 'lmust' so that it > will work? Lifting 'lmust' out of 'get2' doesn't seem to help. > > Thanks, > David > > let must section name = function > | Some o -> o > | None -> Printf.eprintf "Expecting %s in %s\n%!" name section; > exit 1 > > type foo = { a: string; b: int } > > let get1 a b = > { a = must "get1" "a" a; > b = must "get1" "b" b } > > let get2 a b = > (* This isn't polymorphic enough. *) > let lmust = must "get2" in > { a = lmust "a" a; > b = lmust "b" b } > > -- > 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 > -- 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
