RE: [sv-bc] Clarification on space stripping for passed arguments in macros

Hi, Tom.


________________________________

	From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Alsop, Thomas R
	Sent: Friday, August 03, 2007 9:06 PM
	To: sv-bc@server.eda.org
	Subject: [sv-bc] Clarification on space stripping for passed
arguments in macros
	
	

	Just one clarification in this mantis item.  Can we add an
example of "White space before and after the arguments shall be stripped
off"  
	[SB]  OK, I will alter at least one of the examples to show
this. I thought I had done so,  but maybe I forgot.

	
	What happens for example of I do this:

	 

	`D(" msg1","msg2 ")

	 

	Note the white space in the arguments.  

	 

	Do I get this? 

	prints "startmsg1msg2end"

	 

	Or this?

	prints "start msg1msg2 end"

	[SB]  The second, because the arguments are the string literals,
each of which is a single token.

	 

	This leads to another question about using quotations to pass
the argument.  Do we ever expect anyone to want to actually pass a
string with a space prefix or suffix?  In which case it would be nice to
let them do this by explicitly using quotations and making this "space
stripping" enhancement only apply to non-quoted arguments.  So perhaps
this can be clarified as well.  If I have a macro call like this:

	 

	`D(msg1,msg2)

	 

	I assume this is the same as this:

	 

	`D("msg1","msg2")
	[SB] No, it is not, because the second passes the quotation
marks as well. Changing this would break back-compatibility. 

	 

	But what about calls like this:

	 

	`D( msg1,msg2 )

	 

	Would this example be equivalent to this?

	 

	`D(" msg1","msg2 ")
	[SB] No, for the same reason.

	 

	Regards,

	Shalom 

	 

	Thanks, -Tom

	 

	 

	Mantis 1957

	A macro actual argument may be empty

	In P1800-2008/D3a. Section 21.5.1, 

	CHANGE

	To use a macro defined with arguments, the name of the text
macro shall be followed by a list of actual arguments in parentheses,
separated by commas. White space shall be allowed between the text macro
name and the left parenthesis. The number of actual arguments shall
match the number of formal arguments.

	TO

	To use a macro defined with arguments, the name of the text
macro shall be followed by a list of actual arguments in parentheses,
separated by commas. White space shall be allowed between the text macro
name and the left parenthesis. White space before and after the
arguments shall be stripped off before argument substitution into the
macro text. 

	 

	The number of actual arguments shall match the number of formal
arguments. However,  an actual argument may be empty or white space
only, in which case the formal argument is substituted by nothing.
Commas must still be used to maintain the correct number of arguments.

	 

	Example:

	`define D(x,y) initial $display("start", x , y, "end");

	 

	`D("msg1","msg2") // prints "startmsg1msg2end"

	`D("msg1", )      // prints "startmsg1 end"

	`D(,"msg2")       // prints "start msg2end"

	`D(,)             // prints "start  end"

	`D("msg1")        // illegal, only one argument

	`D()              // illegal, only one empty argument

	 

	 


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