2008-09-22-Minutes < P1778

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---+ 22 Sept 2008 - Workgroup Meeting Minutes

   * Workgroup:  P1778 - Esterel v7 language standardization
   * Location:   Teleconference (see [[Next Meeting]] to connect)
   * Date:       22 Sept 2008
   * Chair:      Gerard Berry
   * Vice Chair: Stephen Edwards
   * Secretary:  Sylvan Dissoubray

---++ Attendance

   * Present: Gerard, Marc Perreaut, Sylvan, Ramesh, Eric, Charles, Luigi, Klaus, Raphael, Stephen, Mike, Marc Duranton, Shyam
   * Excused: Claus, Jean-Philippe, Badr
   * See [[Attendance Record]] for meetings participation history


---++ Agenda

   1. Agenda and process
   1. IEEE tkwiki site open 
   1. Statements chapter 
   1. Next meetings

---++ Process

   * *Start*: Chair declares the meeting open at 4:06
   * *Agenda*: The agenda is approved by participants
   * *Minutes*: No objections about last meeting minutes -- they are approved
   * *Patents*: No new item . The page [[IEEE Patent Policy]] holds the call for patent, and workgroup status.

---++ Technical topics

_Brief summary of discussion, pros and cons, and conclusions_

---+++ Statements chapter comments

   * Comments were contributed on the wiki and on annotated pdf by the workgroup (Claus, Ramesh, Luigi, Shyam, ...). All reviewed and discussed during the meeting.

   * General impressions
      * EB: quite clear now.  
      * SE: some imprecisions need to be fixed.
      * MD: comment about tags. semantics is good.
      * SE: semantics at the end ? GB: tradeoff, big chapter this way makes it more readable. Too many examples? (with default, without default).
      * MK: new presentation is nice, in general.

   * Tags: explicit toplevel section, the program conceptually has tags, etc. Move 12.1.4  after 12.2 (belongs to semantics). 

   * KS: 12.1.5 Too detailed?

   * MD explain synchronous earlier than chapter 12 ? Think about what to define in the introductive overview and definitions

   * *Semicolon* Nobody wants semicolon as separator, everybody wants it to be a terminator. Agreed.

   * Brackets must be in syntax rules

   * Traps are necessarily outside parallel add a note 

   * for dopar: shall be positive. If not, it is either a compile-time or run-time error. Better decide what kind of error. Also possible to decide that if not positive then is considered as _nothing_ This seems a better option. Semantics is static expansion, compile-time or run-time: whichever (implementation choice). This question is related to to static_if and static_for. static_for and for (not expanded). The interest is because of the need to generate linear VHDL wrt Esterel source size. 
      * SE: static statements are appreciated (discussed in C++). Just syntactic concern. 
      * do seq has been asked. Only way seems to be static. 
      * static before expression or before statement? nested expressions too complex. 

   * repeat, positive or not. mandatory for dependency analysis. repeat until would be clearer. Think about index usage inside the repeat
      * similar to static discussion

   * clarify delayed suspend defnition

   * concurrent traps (trap T1, T2 in) have been removed to simplify the statements. No practical objection.


   * Discussion about static instructions: 
      * A static instruction, e.g. static if or static for has the same semantics as the non-static form, expect that it requires the intruction to be performed statically, i.e. at compile-time. 
      * The static if instruction is a clean form of #ifdef and makes static run module recursion possible.
      * The static for makes it possible for the user to specify whether the for loop must be expanded at compile-time. The static for is useful to handle carry array dependencies over modules under for loops, which cause static cycles without the compile-time for loop expansion. There are several possible syntaxes:

<verbatim>
static_if e then
...
static if e then
...
if_static e then
...
if static e then
...
</verbatim>

   * Propositions for while-do and do-while instructions
<verbatim
while e do
  p
end while
<=>
trap done in
  loop
    if e then exit done;
    p
  end loop
end trap

do
  p
while e
<=>
trap done in
  loop
    p;
    if e then exit done
  end loop
end trap
</verbatim>

To be experimented before.
We have experiment of "nice" instructions that have been added but never proved to be useful.

   * Constructiveness and causality issues. The standard will say nothing about that. Compiler may have different point of views and accept different programs. The important point is that when a program is accepted by two different compilers, then it does the same.


---++ Motions and actions items with name and due date

---++ Adjournment and Next meeting date

   * Next meeting will be about signals. *Monday 20th October - 4 PM Paris time*
   * Meeting is closed at 5:45 PM.
Topic revision: r4 - 2008-09-25 - 13:34:54 - SylvanDissoubray
P1778