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types of ocamlyacc's entry points
- Virgile Prevosto
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Date: | 2004-11-03 (13:06) |
From: | Virgile Prevosto <virgile.prevosto@m...> |
Subject: | types of ocamlyacc's entry points |
Hello list, I just ran into a problem while trying to parameterize an ocamlyacc-generated parser by a custom parsing function. The .mly file looked like: ----------------------------- %token <string> SPECIAL %start main %type <(string -> 'a) -> 'a> main %% main: SPECIAL { fun specialized_parser -> specialized_parser $1 } %% ------------------------------ ocamlyacc complains: "e - the start symbol main has a polymorphic type". It seems to me that this in contradiction with the manual, which says that "The type part [of a %type directive] is an arbitrary Caml type expression, except that all type constructor names must be fully qualified". So, my first question is: Who is right, the documentation or the implementation? I suspect that this behavior is due to the bug #1583, which showed that such types may lead to unsafe code, but I think that one or two line(s) in the manual would be useful. As a workaround, I've tried to wrap the parser in a functor (this was my first intention in fact, as the custom parsing function should come from a module): ----------------------------- %{ module type Foo = sig type t val from_string: string -> t end module ParseFormula = functor (A: Foo) -> struct %} %token <string> SPECIAL %start main %type <A.t> main %% main: SPECIAL { A.from_string $1 } %% end ------------------------------ While looking like an ugly hack, this seems to work, except that the generated .mli file is not correct (see feature wish #1703 and not a bug #1886). I can ask make to remove it, but is there a cleaner way to proceed (apart from using camlp4 or Stream) ? Many thanks in advance, -- E tutto per oggi, a la prossima volta Virgile