mutable records

Scott J.
Tue, 3 Sep 2002 19:55:22 +0200

Sorry for my late reply,

But is it possible to be more specific (little examples)

In Haskell one can use existential lists but I doubt about the efficiency.

It is not my aim to make of everything an object like in Jave e.g. . The
objects I have in mind are showable ojects: windows, scrollbars,
messageboxes, etc. . Of such objects I demand fast response with respect to
key input or mouse clicks. I am sure Ocamel can do that.


----- Original Message -----
From: "Manuel M T Chakravarty" <>
To: <>
Cc: <>
Sent: Tuesday, September 03, 2002 10:37 AM
Subject: Re: mutable records

> "Scott J." <> wrote,
> > Is it possible to define  oject types in Haskell and what does one
propose to do it?
> Depends on what you mean by object types.  You can surely
> define a record with funcions dubbing as methods and
> non-functional values dubbing as object data.
> > Is it possible to define parts of a record  with the help of the ST s
monad mutable during the whole program? (As is possible in Ocamel)?
> Just make the fields that you want to update be values of
> `STRef s a'.  (You can also do the same with the IO monad
> and `IORef's.)
> Having said this, there are not that many situations where
> you need to do this (and in consequence ST-monadify your
> program).  Purely functional updates (using the record
> syntax) where the system effectively copies the whole record
> (not all data in it, just the references to that data) is
> perfectly suitable in most cases.  If you are concerned
> about efficiency first profile the code to see whether the
> performance bottleneck is really where you think it is.
> Cheers,
> Manuel