deftype & type - Where are they documented?

Thomas Arts <>
Fri Nov 22 08:44:34 CET 2002

Dear all

The specweb development has stopped for a while ago. Nevertheless, I
have always used it for the development of my own code. I find it convenient
to have type annotations in my code.

However, specweb doesn't help you in checking that the annotations are
correct. There is no checking that your type annotation should change if you
change your function. Thus, in general one has to do all the tuning by hand.

After that Joe and I have left Ericsson, there is nobody working on type
inside the company. However, there are several people at universities
that now and then try to look into this rather complicated problem.

We cannot expect much type checking for Erlang in the very
near future. If, though,  you would like to experiment with type
annotations and you would like to typecheck an annotated program,
then please send it to me and I can see what I can do for you.

Best regards

FMICS 03, June 5-7 in Trondheim.
Call for papers:

Dr Thomas Arts
     Program Manager
     Software Engineering and Management
IT-university of Gothenburg
Box 8718, 402 75 Gothenburg, Sweden

Tel +46 31 772 6031
Fax +46 31 772 4899

----- Original Message -----
From: "Chris Pressey" <>
To: "isaac gouy" <>
Cc: <>
Sent: Friday, November 22, 2002 2:13 AM
Subject: Re: deftype & type - Where are they documented?

> On Thu, 21 Nov 2002 12:24:00 -0800 (PST)
> isaac gouy <> wrote:
> > +deftype continuation(T) = {} | {T,
> > fun(T,continuation(T)) -> continuation(T)}.
> >
> > +type seq(int(),int()) -> continuation(int()).
> >
> >
> > I haven't figured out where deftype or type are
> > mentioned in the Erlang documentation or book. Where
> > can I find out about this?
> They're part of the Specification Web type system, seperate from Erlang
> itself.  It seems to be documented at:
> but I don't know if it's up to date...
> -Chris

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