[M3devel] A question for our language lawyers

[Dragiša Durić]

Dirk,

If you still have doubts, you are better man than most of us :)

Thanks in advance!

On Jul 6, 2012, at 9:54 PM, Dirk Muysers wrote:

> Daniel, with my apologies, sometimes I wonder if you do it on purpose.
> 
> From: Daniel Alejandro Benavides D.
> Sent: Friday, July 06, 2012 9:17 PM
> To: m3devel at elegosoft.com ; Rodney M. Bates
> Subject: Re: [M3devel] A question for our language lawyers
> 
> Hi all:
> English men say array is a sequence of elements (of a common type), and a BOOLEAN is an enumeration so you might attack that distinction to define what is an initialized boolean or array of boolean in common compilers, gcc javac, etc, which if is java-like is really undefined:
> 
> http://www.drdobbs.com/architecture-and-design/the-humble-boolean-deserves-help/232900836?cid=DDJ_nl_upd_2012-05-02_h&elq=cef656ee4d6c4bca996b337620b98f85
> 
> So I prefer non-uniform rules for records different of Sets, Arrays, and records as that, note that NEW expression doesn't allow constructors to be used, so the only thing you can use is array of uninitialized variables (but current gcc or javac, etc are really wrong in that)
> 
> This means we need to address this by either a native backend (NT386) or by another language for that matter.
> 
> Thanks in advance for any comments you may have
> 
> --- El vie, 6/7/12, Rodney M. Bates <rodney_bates at lcwb.coop> escribió:
> 
> De: Rodney M. Bates <rodney_bates at lcwb.coop>
> Asunto: Re: [M3devel] A question for our language lawyers
> Para: m3devel at elegosoft.com
> Fecha: viernes, 6 de julio, 2012 13:27
> 
> 
> 
> On 07/06/2012 04:23 AM, Dirk Muysers wrote:
> > The report says (2.6.9)
> > "The values in the array will be arbitrary values of their type."
> 
> > Now, ParseParams in its "init" method allocates an array of BOOLEANs
> > and relies on the fact that it is supposedly initialised with FALSE values.
> 
> > At the other hand the report says (2.2.4)
> > "The constant |default| is a default value used when a record is constructed or allocated"
> 
> > If I allocate an array of records, which statement is stronger:
> > - the array contains arbitray record values ?
> > - the array record fields will be initialised to their default values?
> 
> Admittedly unclearly if not misleadingly worded.  Better wording might be
> to say each element is initialized as it would if it were a scalar variable
> of its type.
> 
> I think the way to interpret this is that the array itself does not impose
> any initialization, but this fact will not eliminate initialization
> imposed by other rules, specifically, the type of the array's elements.
> 
> This is a language quirk that I have always been deeply ambivalent about.
> The type safety would go down the drain if variables were not initialized
> to a bit pattern that represents some value of the type, so we have to pay
> the performance penalty of executing initialization code.  So why not define
> which value of the type is initialized-to and get behavioral predictability
> for free?  And further save redundant initialization in the likely event
> that the compiler's chosen arbitrary value happens to match what the
> programmer wants?
> 
> (OK, a smart enough optimizer might figure this out, but we could have
> had it even with a naive compiler.)
> 
> The contrary case is a type whose compiler-chosen representation happens
> to use every bit pattern in the allocated space for a value of the type.
> Here, no compiler-generated runtime initialization is needed.
> 
> Also, the rule we have might sometimes encourage programmers to at least give a
> millisecond's thought to whether they need to do some explicit initialization.
> 
> 
> > The ParseParams "init" method is obviously erroneous and works only
> > by virtue of a happy combination of circumstances.
> > But how is the report to be interpreted in the second case?

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://m3lists.elegosoft.com/pipermail/m3devel/attachments/20120706/c4e6ee82/attachment-0002.html>