Your own behaviours

Chandrashekhar Mullaparthi Chandrashekhar.Mullaparthi@REDACTED
Tue Sep 25 00:50:06 CEST 2001

I tried looking at the documentation but couldn't find it - is it possible
for a module to implement more than one behaviour?? I don't have an example
of why I would need to do this but it occured to me that it can be quite
powerful for a process to implement different behaviours. A bit like a class
implementing a number of interfaces in Java.

I haven't programmed much in Java so I dont quite know how useful this
ability is - but if someone has experience with this I'd like to hear what
they think.


> -----Original Message-----
> From: Gunilla Hugosson [mailto:gunilla@REDACTED]
> Sent: 21 September 2001 13:07
> To: erlang-questions@REDACTED
> Subject: Re: Your own behaviours
> Hi,
> This feature has now been added to Erlang/OTP R8 according to
> an implementation proposal made by Ulf Wiger. Release note:
> 	It is now possible to have the compiler check user-defined
> 	behaviours and not only the pre-defined OTP behaviours
> 	(gen_server etc.).
> 	This is done by adding a function behaviour_info/1 to
> 	the behaviour module. behaviour_info(callbacks) should return
> 	a list of {FunctionName,Arity} which defines the callback
> 	functions the behaviour uses.
> 	When a callback module with the attribute
> 	  -behaviour(Behaviour).
> 	is compiled, its exported functions will be compared with
> 	the list returned by Behaviour:behaviour_info(callbacks) and
> 	a warning will be issued if any callback function is missing.
> 	Note that the user must ensure that the module Behaviour is
> 	present at compile-time and can be found in the current code
> 	path.
> Best regards, Gunilla
> Lennart Öhman wrote:
> > Hi!
> > 
> > Mandatory callback functions, among other things, are defined
> > in the module otp_internal. This module is used when compiling
> > modules having -behavior attribute.
> > 
> > If you wish to extend your OTP with your own behaviors, otp_internal
> > must (should) be changed.
> > 
> > My suggestion is that the functions in the otp_internal are 
> changed to
> > look for the "answers" in the generic module corresponding
> > to the behaviour at hand. In this way you do not need to change
> > modules belonging to the original system. But instead only program
> > a set of required functions in any new behaviour you invent.
> > 
> > Best Regards,
> > 
> > Lennart
> > 
> > -------------------------------------------------------------
> > Lennart Ohman                   phone   : +46-8-587 623 27
> > Sjoland & Thyselius Telecom AB  cellular: +46-70-552 6735
> > Sehlstedtsgatan 6               fax     : +46-8-667 8230
> > SE-115 28 STOCKHOLM, SWEDEN     email   : lennart.ohman@REDACTED
> -- 
> _____Gunilla Hugosson____________________________________________
> Project Manager, Erlang/OTP
> Ericsson Utvecklings AB, UAB/S/P OTP Product Development
> gunilla@REDACTED  +46-8-7275730

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