Subject: SDL-News: Rick's confirmation of interfaces
From: William H. Skelton (W.Skelton#SOLINET.com)
Date: Wed Nov 26 2003 - 14:26:33 GMT
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-----From "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews -----
Dear Rick,
Thank you for clarifying this point, which is much appreciated!
You may justly point the finger at me that I couldn't find it, but in my
defence I was not alone! At the beginning of October an old SDL hand (much
more experienced than me, a mere junior in comparison) and I looked at the
latest specification and concluded it wasn't possible!
In fact we hadn't abandoned all hope, only deferred it; just as well we
mentioned it again... :-)
So now you have opened the door of enlightenment for us, the task force is
one step closer to harmonizing this issue.
To summarise, should the task force subset use a subset of interfaces
instead of signal lists?
As I understand it, the subset of interfaces would be that an interface is
defined as a list of signals with their parameters.
Gates would be declared with the name of an interface instead of a signal
list. In fact, signal lists could be deleted from the subset.
I assume previous comments about using signal lists as a data-type, then
would be applicable to interfaces instead. Is this right, Keith?
Comments welcome...
BTW, there is no need to use my email address directly;
Members#SDL-Task-Force.org is copied to me and all the other task force
members! :-)
William
>Date: Wed, 26 Nov 2003 11:57:00 +0000
>Subject: Re: [SDLTF-Members] possible extension to SDL
>From: Rick Reed TSE <rickreed#tseng.co.uk>
>To: <members#sdl-task-force.org>
>CC: <sdlnews#sdl-forum.org>
>
>William H. Skelton at W.Skelton#SOLINET.com wrote on 26/11/2003 01:18:
>
> > 2) In the draft specification we have discussed that the definition of
> > signals used in a signal list should be declared within the signal list,
> > i.e. as belonging to that signal list. Something we tighten up in the
> subset.
> >
> > Unfortunately it seems the syntax doesn't allow this. There was a glimmer
> > of hope that the new INTERFACE syntax of SDL-2000 would allow signals to be
> > declared within the INTERFACE, but on checking the SDL-2000 specification
> > it seems it also doesn't allow it either.
>
>Dear All,
>
>The syntax for interfaces DOES allow signals to be defined in interfaces.
>
>
>
>NOTE: the syntax in this email is best viewed with a fixed width font.
>
>The full syntax in the SDL-2000 language definition is:
>
><interface definition> ::=
> {<package use clause>}*
> [<virtuality>] <interface heading>
> [<interface specialization>] <end>
> | {<package use clause>}*
> [<virtuality>] <interface heading>
> [<interface specialization>] [ <comment body> ] <left curly bracket>
> <entity in interface>* [<interface use list>]
> <right curly bracket>
>
><interface heading> ::=
> interface <interface name>
> [<formal context parameters>] [<virtuality constraint>]
>
><entity in interface> ::=
> <signal definition>
> | <interface variable definition>
> | <interface procedure definition>
> | <exception definition>
>
>The difference between the two alternatives of <interface definition> are
>better seen by rewriting the syntax as:
>
><interface definition> ::=
> {<package use clause>}*
> [<virtuality>] <interface heading>
> [<interface specialization>]
> { <end>
> | [ <comment body> ] <left curly bracket>
> <entity in interface>* [<interface use list>]
> <right curly bracket>
> }
>
>Ignoring package use, virtuality, specialization and the comment before the
>left curly bracket this becomes:
>
><interface definition> ::=
> <interface heading>
> { <end>
> | <left curly bracket>
> <entity in interface>* [<interface use list>]
> <right curly bracket>
> }
>
>The <interface heading> would normally be just the keyword INTERFACE
>followed by the defining occurrence of the interface name, such as:
>
>INTERFACE LineOut
>
>One of the alternatives of <entity in interface> is <signal definition>, so
>to define a LineOut interface with signals Establish(Path),
>Send(DataPacket), Release(Path) can be written:
>
>INTERFACE LineOut { SIGNAL Establish(Path),
> Send(DataPacket),
> Release(Path);
> }
>
>where Path and DataPacket are data types defined somewhere.
>
>William: Which version of Z.100 did you use?
>
>--
>Rick Reed - rickreed#tseng.co.uk
>Tel:+44 15394 88462 Mob.:+44 7970 50 96 50
------------------------------------------------------------------------
William H. Skelton, Engineering Dept.
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--End text from "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews ---
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