0000778: type constraints and interface files

(0000119)
administrator (administrator)
2002-01-07 08:25

> Full_Name: Dan Arnon
> Version: 3.02

> The type constraint at the end of the type of module Y looks cyclic, but it
> shouldn't be: it basically means
> that the type t of Y should be the same as the type t of X. The compiler
seems
> to understand that and it compiles this without any complaint. However, the
.mli
> file that it creates looks a bit different:
>
> module type X =
> sig
> type t
>
> module Y :
> sig
> type t = t
> end
> end
>
> This is just another way to express the same constraint. So far so good.

No: this one is cyclic. The only proper way to describe your type is probably
your original definition. But it would be really messy to have the
pretty-printer do that, so you will have to correct the .mli by hand until
somebody finds a better way.

A simple workaround is either to use another name for your type, or to put the
first ocurrence in another submodule.

i.e.
  module type X = sig
    module T : sig type t end
    module Y : sig type t = T.t end
  end
  module type X' = X with type T.t = int

Jacques Garrigue

(0000120)
administrator (administrator)
2002-01-07 08:26

Silly printing problem. Use workaround.

(0006612)
doligez (manager)
2012-01-06 15:39

The pretty-printer is not absolutely guaranteed to output correct OCaml code.
This would be pretty hard to fix, and the problem is really small.

This won't be fixed in the forseeable future.

Issue History
Date Modified	Username	Field	Change
2005-11-18 10:13	administrator	New Issue
2012-01-06 15:39	doligez	Note Added: 0006612
2012-01-06 15:39	doligez	Status	acknowledged => resolved
2012-01-06 15:39	doligez	Resolution	open => suspended
2012-01-06 15:39	doligez	Description Updated	View Revisions

Notes
(0000119) administrator (administrator) 2002-01-07 08:25	> Full_Name: Dan Arnon > Version: 3.02 > The type constraint at the end of the type of module Y looks cyclic, but it > shouldn't be: it basically means > that the type t of Y should be the same as the type t of X. The compiler seems > to understand that and it compiles this without any complaint. However, the .mli > file that it creates looks a bit different: > > module type X = > sig > type t > > module Y : > sig > type t = t > end > end > > This is just another way to express the same constraint. So far so good. No: this one is cyclic. The only proper way to describe your type is probably your original definition. But it would be really messy to have the pretty-printer do that, so you will have to correct the .mli by hand until somebody finds a better way. A simple workaround is either to use another name for your type, or to put the first ocurrence in another submodule. i.e. module type X = sig module T : sig type t end module Y : sig type t = T.t end end module type X' = X with type T.t = int Jacques Garrigue

(0000120) administrator (administrator) 2002-01-07 08:26	Silly printing problem. Use workaround.

(0006612) doligez (manager) 2012-01-06 15:39	The pretty-printer is not absolutely guaranteed to output correct OCaml code. This would be pretty hard to fix, and the problem is really small. This won't be fixed in the forseeable future.

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