Re: [sv-bc] Variable number of arguments to macros

I can't support this proposal.

A couple of quick concerns/questions:
   1) what is the point of argc unless you have compile time loops
      and conditionals?  I know that some people want that as
      well, but such a change is going to require a complete
      overhaul of the macro system.
   2) I don't particularly like having the indexing operations
      be indistinguishable from expansion text.  I am worried
      about the implications of when and how one deals with
      composition, etc.  With:
         `define B [0]
         Q`B
      what does Q[0] mean?  What if I token-pasted the [0]?  etc.
   3) If you have:
         `define F(V...) `G(V)
      does the "V" expand to multiple arguments to G or is it
      a single argument including the commas?

I have general uneasiness with other interactions that I'd
have to think about further before having specifics but at
this point I can't support this proposal.  I think this needs
to wait for the next PAR.

Gord.



Bresticker, Shalom wrote:
> Mantis 1566 is a request to allow a variable number of arguments to 
> tasks/functions, macros, etc. It is on our list.
> 
> Attached is a proposal for variable number of arguments to macros.
> <<1566_D4_macros.V2.htm>>
> Thanks,
> Shalom
> 
> Shalom Bresticker
> Intel Jerusalem LAD DA
> +972 2 589-6582
> +972 54 721-1033
> 
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> 
> Mantis 1566-macros
> 
> P1800-2008/D4
> 
> Add variable number arguments to text macros
> 
> The proposal is based on Mantis 1571
> 
> In Section 21.5.1
> 
> CHANGE
> 
> Change the syntax in Syntax 21-2 from (FROM MANTIS 1571)
> 
> list_of_formal_arguments ::=
>     formal_argument { , formal_argument }
> formal_argument ::=
>     simple_identifier [ *=* default_text ]
> 
> TO
> 
> list_of_formal_arguments ::=
>     formal_argument { , formal_argument } [ , last_format_argument ]
> formal_argument ::=
>     simple_identifier [ = default_text ]
> last_format_argument ::=
>     simple_identifier ... [ = default_text ]
> 
> 
> CHANGE (TEXT FROM MANTIS 1571)
> 
>  
> 
> If formal arguments are used, the list of formal argument names shall be 
> enclosed in parentheses following
> 
> the name of the macro. The formal argument names shall be 
> /simple_identifiers/, separated by commas and
> 
> optionally whitespace. The left parenthesis shall follow the text macro 
> name immediately, with no space in between.
> 
>  
> 
> A formal macro argument may have a default. A default is specified by 
> appending an = token after the formal argument name, followed by the 
> default text. The default text is substituted for the formal argument if 
> no corresponding actual argument is specified.
> 
> The default text may be explicitly specified to be empty by adding an = 
> token after the formal argument name, followed by a comma (or a right 
> parenthesis if it is the last argument in the argument list.)
> 
> 
> TO
> 
>  
> 
> If formal arguments are used, the list of formal argument names shall be 
> enclosed in parentheses following
> 
> the name of the macro. The formal argument names shall be 
> /simple_identifiers/, separated by commas and
> 
> optionally whitespace. The left parenthesis shall follow the text macro 
> name immediately, with no space in between.
> 
> 
> A formal macro argument may have a default. A default is specified by 
> appending an = token after the formal argument name, followed by the 
> default text. The default text is substituted for the formal argument if 
> no corresponding actual argument is specified.
> 
> The default text may be explicitly specified to be empty by adding an = 
> token after the formal argument name, followed by a comma (or a right 
> parenthesis if it is the last argument in the argument list.)
> 
> The last argument in the list of formal argument names may be followed 
> by an ellipsis (...) and  is then called a /multiple argument/. In that 
> case, a list of actual arguments, separated by commas, may be specified 
> in the argument list in the text macro call. The list of actual 
> arguments, including the commas, shall be subsituted for the formal 
> multiple argument in the macro text. A default may be specified for a 
> formal multiple argument as well, after the ellipsis. Such a default may 
> itself be a multiple argument list.
> 
> Within the scope of the macro text, the predefined macro `__ARGC__ 
> designates the number of arguments specified in the multiple argument 
> list (or of the default if the default was used). A particular member of 
> the multiple argument list may be specified by appending a simple 
> non-negative integer constant index within square brackets to the 
> multiple argument list name. The arguments in the multiple argument list 
> are numbered from 0 to `__ARGC__ -1 . It shall be an error to specify a 
> number beyond the end of the list.
> 
>  
> 
> CHANGE
> 
>  
> 
> It shall be an error to specify more actual arguments than the number of 
> formal arguments. (FROM Mantis 1571)
> 
> TO
> 
> It shall be an error to specify more actual arguments than the number of 
> formal arguments unless the last formal argument is a multiple argument.
> 
>  
> 
>  
> 
> CHANGE (TEXT FROM Mantis 1571)
> 
>  
> 
> Example without defaults:
> 
>  
> 
> ...
> 
>  
> 
> Example with defaults:
> 
> ...
> 
> TO (ADD NEW EXAMPLES AFTER OTHER EXAMPLES)
> 
> Example without defaults:
> 
>  
> 
> ...
> 
>  
> 
> `define MUTEX(name, V...) name: assert($onehot0{V})
> 
> `MUTEX (one_driver, a,b,c);
> 
>             // expands to "one_driver: assert($onehot0{a,b,c});
> 
>  
> 
> `define HEAD(Q...) Q[0]
> 
> `HEAD(3,1,4,15) // evaluates to 3
> 
> Example with defaults:
> 
> `define MUTEX(name, V...=a,b) name: assert($onehot0{V})
> 
> `MUTEX (one_driver);
> 
>             // expands to "one_driver: assert($onehot0{a,b});
> 
>  
> 

-- 
--------------------------------------------------------------------
Gordon Vreugdenhil                                503-685-0808
Model Technology (Mentor Graphics)                gordonv@model.com


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