RE: [sv-bc] Mantis 1602: task/function inout arg defaults - draft proposal

Dave,


________________________________

	From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Rich, Dave
	Sent: Wednesday, August 15, 2007 9:33 AM
	To: Bresticker, Shalom; sv-bc
	Subject: RE: [sv-bc] Mantis 1602: task/function inout arg
defaults - draft proposal
	
	

	Hi Shalom,

	 

	This still does not explain when the default expression is
applied to an output, 
	[SB] The section quoted in the proposal does not explain when
the default expression is applied to an input either. That explaination
follows later in the following paragraph, which says, 

	[SB] "When the subroutine is called, arguments with default
values can be omitted from the call, and the compiler shall insert their
corresponding values. Unspecified (or empty) arguments can be used as
placeholders for default arguments, allowing the use of nonconsecutive
default arguments. If an unspecified argument is used for an argument
that does not have a default value, a compiler error shall be issued."  

	Maybe we should change the phrase "default value" in that
paragraph, since in the case of inouts, outputs, and ref's, it is not
really a value.

	 

	 or why you would want to use one. 
	[SB] This was discussed in the previous SV-BC meeting, and the
majority was in favor of allowing output defaults, so your argument is
not with me. I just asked what the majority opinion was. If you ask what
I would use it for, I would say that it is just like any other default.
That is, if I would often call the subroutine using the same actual
argument for this output, then a default would be useful so that I would
not have to write it explicitly each time, just as with an input.

	 

	 If the only purpose is to leave the output unconnected, why
don't we use something like

	 

	output/inout int arg = null; 

	 

	to say that the output may be discarded if left unconnected.
	[SB] In the SV-BC meeting, several ways of leaving an output
unconnected were discussed, and there was not general agreement on any
particular way. Yours is one. I wanted to get agreement on output
defaults in general before extending them to allow unconnected outputs.
I guess one could use 'null' as an actual output argument as well, in
order to explicitly unconnect it.

	 

	We probably should only allow const ref arguments, not ref
arguments to specify a default.
	[SB] Again, the general feeling of the committee was different. 

	 

	I liked the original wording about the default expression being
bound to the declaration scope. I don't like words like "as though" to
describe behavior.
	[SB] My proposal essentially preserves that original wording.
The original said,

	"The expression is evaluated in the scope containing the
subroutine declaration."

	My proposal has the wording,

	"the default expression is evaluated in the scope containing the
subroutine declaration, not in the scope containing the subroutine
call."

	 

	The additional sentence that I added that you refer to is,

	"the call is treated as though the default had been written
explicitly in the subroutine call."

	 

	The reason I added that sentence is that the phrase, "the
expression is evaluated" gives the impression that its value is
evaluated and its value is used. That makes sense for an input, but not
for an ouput, inout, or even a const ref.

	 

	Thanks,

	Shalom

	 

	
________________________________


	From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Bresticker, Shalom
	Sent: Tuesday, August 14, 2007 10:44 PM
	To: sv-bc
	Subject: FW: [sv-bc] Mantis 1602: task/function inout arg
defaults - draft proposal

	 

	Hi,

	 

	I did not get any responses to this.

	 

	Please comment.

	 

	Thanks,

	Shalom

	 

	
________________________________


	From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Bresticker, Shalom
	Sent: Friday, August 03, 2007 6:29 PM
	To: sv-bc
	Subject: [sv-bc] Mantis 1602: task/function inout arg defaults -
draft proposal

	<<1602_D3a.doc>> 
	Hi, 

	I have attached a draft proposal for Mantis 1602, clarifying the
behavior of subroutine inout argument defaults and also allowing output
defaults. It still does not cover allowing output arguments to be
unconnected. Please comment.

	The phrasing about identifiers in the defaults being bound from
the scope of the subroutine declaration is the same as the original
phrasing, but I feel it is not clear enough and requires some examples
to clarify it.

	Thanks, 
	Shalom 

	Shalom Bresticker 
	Intel Jerusalem LAD DA 
	+972 2 589-6852 
	+972 54 721-1033 

	
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