0005714: Syntax error in the signature of recursive module definitions generated by 'ocamlxxx -i'

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0005714

OCaml

OCaml typing

public

2012-08-03 11:18

2012-08-03 12:07

Reporter

giavitto

Assigned To

lefessan

Priority

normal

Severity

minor

Reproducibility

always

Status

resolved

Resolution

no change required

Platform

MAC

OS X

OS Version

10.7

Product Version

4.00.0

Target Version

Fixed in Version

Summary

0005714: Syntax error in the signature of recursive module definitions generated by 'ocamlxxx -i'

Description

The signature of a recursive module definition raises a syntax error. It happens with the signature generated by "ocamlc -i" from a recursive module definitions. And I was unable to find the "right way" to define the signature by hand.

Steps To Reproduce

One can use the signature given in example in the documentation (http://caml.inria.fr/pub/docs/manual-ocaml/manual021.html#toc75 [^]):

module rec A : sig
                     type t = Leaf of string | Node of ASet.t
                     val compare: t -> t -> int
                   end
        and ASet : Set.S with type elt = A.t

which gives
  Error: Syntax error
at a position corresponding to the "and".

The signature also be produced from of a recursive module definition using "ocamlc -i". For the example in the documentation, it gives:

module rec A :
  sig
    type t = Leaf of string | Node of ASet.t
    val compare : t -> t -> int
  end
and ASet :
  sig
    type elt = A.t
    type t
    val empty : t
    val is_empty : t -> bool
    val mem : elt -> t -> bool
    val add : elt -> t -> t
    val singleton : elt -> t
    val remove : elt -> t -> t
    val union : t -> t -> t
    val inter : t -> t -> t
    val diff : t -> t -> t
    val compare : t -> t -> int
    val equal : t -> t -> bool
    val subset : t -> t -> bool
    val iter : (elt -> unit) -> t -> unit
    val fold : (elt -> 'a -> 'a) -> t -> 'a -> 'a
    val for_all : (elt -> bool) -> t -> bool
    val exists : (elt -> bool) -> t -> bool
    val filter : (elt -> bool) -> t -> t
    val partition : (elt -> bool) -> t -> t * t
    val cardinal : t -> int
    val elements : t -> elt list
    val min_elt : t -> elt
    val max_elt : t -> elt
    val choose : t -> elt
    val split : elt -> t -> t * bool * t
  end

which causes a syntax error located at the "and"

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Notes
(0007882) frisch (developer) 2012-08-03 11:25	These are valid signature items. If you put these fragments in an .mli file, or within a "module type S = sig ... end", they work ok. You're looking for a way to define recursive module types, and as far as I know, this is not possible.

(0007883) giavitto (reporter) 2012-08-03 11:38	Oups, you're right. This signature works in a .mli file (but then, why not in a .ml file ?). > You're looking for a way to define recursive module types Definitively. I have some complex interdependencies between types in several modules. I was hopping to define them by direct recursion. It seems that this approach is not possible.

(0007884) frisch (developer) 2012-08-03 11:56	> This signature works in a .mli file (but then, why not in a .ml file ?). Because signature items are not a subset of structure items. For the same reason, you cannot write val x : int in an .ml file.

Issue History
Date Modified	Username	Field	Change
2012-08-03 11:18	giavitto	New Issue
2012-08-03 11:25	frisch	Note Added: 0007882
2012-08-03 11:38	giavitto	Note Added: 0007883
2012-08-03 11:56	frisch	Note Added: 0007884
2012-08-03 12:07	lefessan	Status	new => resolved
2012-08-03 12:07	lefessan	Resolution	open => no change required
2012-08-03 12:07	lefessan	Assigned To	=> lefessan