defining recursive types with camlp4

defining recursive types with camlp4

[Jacques Le Normand]

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Hello ocaml list,
I have a list of name constructor pairs and from that list I want to define
a set of recursive types. I've written the following function:

let type_chain _loc  lst =
  let rec iter sofar =
    function
      | [] -> sofar
      | (name,constructors) :: ys ->
      iter <:str_item< $sofar$ and $lid:name$ = $constructor$  >> ys
  in
    match lst with
    (name,constructors) :: ys ->
      iter <:str_item< type $lid:name$ = $constructors$ >> ys
      | _ -> raise (Failure "no types defined")

which, unfortunately, fails to type check with the error:

"
While expanding quotation "str_item" in a position of "expr":
  Parse error: illegal begin of quotation of structure item
"

how would I go about writing such a function?

--Jacques L

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Re: [Caml-list] defining recursive types with camlp4

[blue storm]

On Sun, Jun 14, 2009 at 11:10 PM, Jacques Le
Normand<rathereasy@gmail.com> wrote:
> how would I go about writing such a function?

The "... and ..." multiple-declaration isn't at the str_item level but
at the ctyp level. You should use <:ctyp< $..$ and $...$ >>. Moreover,
it appears that the type declaration node in the AST (Ast.TyDcl) does
not have a quotation syntax : <:str_item< type $..$ = $...$ >> won't
work.

  let type_chain _loc  lst =
    let decl (name, constructors) = Ast.TyDcl(_loc, name, [],
constructors, []) in
    <:str_item< type $Ast.tyAnd_of_list (List.map decl lst)$ >>