Re: [sv-ac] question on subroutines on empty sequences

Hi Tej:

I agree with you, and you made the point much more succinctly than
I did.

J.H.

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> Thread-Topic: [sv-ac] question on subroutines on empty sequences
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> From: "Singh, Tej" <tej_singh@mentor.com>
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> Hi Lisa,
> =20
> In the formal semantics appendix
> =20
> (R, v =3D e) is derived as (R ##0 (1, v =3D e))
> =20
> Although this rule applies to local var assignment, I would extend it
> for match items too.
> =20
> (R, match_item_statement) is derived as (R ##0 (1,
> match_item_statement))
> =20
> So if R is empty, match_item_statement should not be executed since=20
> it becomes (empty ##0 (1, match_item_statement)) which does not result
> in match.
> =20
> Tej
> 
> 
> ________________________________
> 
> 	From: owner-sv-ac@server.eda.org
> [mailto:owner-sv-ac@server.eda.org] On Behalf Of Lisa Piper
> 	Sent: Wednesday, January 03, 2007 3:41 PM
> 	To: sv-ac@server.eda-stds.org
> 	Subject: [sv-ac] question on subroutines on empty sequences
> =09
> =09
> 
> 	I have a question. If there is a "sequence_match_item"
> associated with a potentially empty sequence, does it get executed when
> the sequence is empty?  Given the example in the std, there could be a
> sequence_match_item associated with the potentially empty seq
> (potentially empty meaning  a repetition range like [*0:3])  and also a
> sequence_match_item associated with the "seq".  Are both executed
> simultaneously?
> 
> =09=20
> 
> 	Starting on page 293 of the document, page 259 of the pdf,  it
> states:
> 
> =09=20
> 
> 	" Using 0 as the repetition number, an empty sequence results,
> as follows:
> 
> 	a [*0]
> 
> =09=20
> 
> 	An empty sequence is one that does not match over any positive
> number of clock ticks. The following rules
> 
> 	apply for concatenating sequences with empty sequences. An empty
> sequence is denoted as empty, and a
> 
> 	sequence is denoted as seq.
> 
> 	- (empty ##0 seq) does not result in a match.
> 
> 	- (seq ##0 empty) does not result in a match.
> 
> 	- (empty ##n seq), where n is greater than 0, is equivalent to
> (##(n-1) seq).
> 
> 	- (seq ##n empty), where n is greater than 0, is equivalent to
> (seq ##(n-1) 'true).
> 
> =09=20
> 
> 	For example:
> 
> 	b ##1 ( a[*0] ##0 c)
> 
> 	produces no match of the sequence.
> 
> =09=20
> 
> 	b ##1 a[*0:1] ##2 c
> 
> 	is equivalent to
> 
> 	(b ##2 c) or (b ##1 a ##2 c)
> 
> =09=20
> 
> 	Lisa
> 
> =09=20
> 
> 

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