[Caml-list] ICFP 2011: Call for participation

[Caml-list] ICFP 2011: Call for participation

[Wouter Swierstra]

=====================================================================
                      Call for Participation

          The 16th ACM SIGPLAN International Conference
              on Functional Programming (ICFP 2011)

                  http://www.icfpconference.org/icfp2011/
                    Tokyo, Japan September 19-21, 2011
=====================================================================

ICFP provides a forum for researchers and developers to hear
about the latest work on the design, implementations, principles, and
uses of functional programming. The conference covers the entire
spectrum of work, from practice to theory, including its peripheries.

 * Program:
   http://www.icfpconference.org/icfp2011/program.html

 * Registration link:
   https://regmaster3.com/2011conf/ICFP11/register.php

 * Local arrangements (including travel and accommodation):
   http://www.biglab.org/icfp11local/index.html


Schedule including related events:

  September 18
    Workshop on Generic Programming (WGP)
    Workshop on High-Level Parallel Programming and Applications (HLPP)
    Workshop on ML
  September 19-21
    ICFP
  September 22
    Commercial Users of Functional Programming – Day 1 (CUFP Tutorials)
    Haskell Symposium
  September 23
    Commercial Users of Functional Programming – Day 2 (CUFP Tutorials)
    Erlang Workshop
    Haskell Implementors' Workshop
  September 24
    Commercial Users of Functional Programming – Day 3 (CUFP Talks)
    Continuation Workshop

Conference organizers:

 * General Co-Chairs:
     Manuel Chakravarty, University of New South Wales
     Zhenjiang Hu, National Institute of Informatics
 * Program Chair:
     Olivier Danvy, Aarhus University
 * Local Arrangements Chair:
     Soichiro Hidaka, National Institute of Informatics
 * Workshop Co-Chairs:
     Gabriele Keller, University of New South Wales
     Derek Dreyer, MPI-SWS
 * Programming Contest Chair:
     Eijiro Sumii, Tohoku University
 * Publicity Chair:
     Wouter Swierstra, Radboud Universiteit Nijmegen

=====================================================================

Re: [Caml-list] ICFP 2011: Call for participation

[Polux Moon]

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Hi,

I have a type error on code similar to :

-----
type 'par t = 'par

let ident v = v

class alias =
object
  method alias : 'a . 'a t -> 'a = ident (* type error here *)
end
-----

Which gives :

-----
Error: This expression has type 'a. 'a t -> 'a
       but an expression was expected of type 'b. 'b t -> 'b
       Type 'a a = 'a is not compatible with type 'b t = 'b
-----

The problem is related to unification of foralls containing named type in a
method.
The compiler accepts equivalent code when not using the named type "t" or
when not using a method (see attached file).

Is it a [known] limitation ? Is there a way to work around it ?

[-- Attachment #1.2: Type: text/html, Size: 817 bytes --]

[-- Attachment #2: forallclass.ml --]
[-- Type: text/x-ocaml, Size: 300 bytes --]

type 'par t = 'par

let ident v = v (* here adding : 'a . 'a a -> 'a changes nothing *)

class alias =
object
  method alias : 'a . 'a t -> 'a = ident (* NOT OK *)
end

(* but *)
let alias : 'a . 'a t -> 'a = ident (* OK *)
type r = { alias : 'a . 'a t -> 'a}
let alias = { alias = ident } (* OK *)