Subject: RE: [sv-ec] Clarification of INSIDE operator
From: David W. Smith (David.Smith@synopsys.com)
Date: Thu Nov 20 2003 - 16:07:02 PST
Greetings,
Since the SV-BC is working on modifications to the description and
generalization of the insize operator I would recommend that this be
coordinated with the errata proposal that I just forwarded to SV-EC from
Dave Rich. It would be nice to do this as a single set of changes so we do
not end up with inconsistencies.
Regards
David
-----Original Message-----
From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of Arturo
Salz
Sent: Wednesday, November 19, 2003 1:21 PM
To: Ryan, Ray; 'sv-ec@server.eda.org'
Subject: Re: [sv-ec] Clarification of INSIDE operator
Ray,
My comments in purple below.
Arturo
----- Original Message -----
From: Ryan, Ray <mailto:Ray_Ryan@mentorg.com>
To: 'sv-ec@server.eda.org'
Sent: Tuesday, November 18, 2003 2:45 PM
Subject: [sv-ec] Clarification of INSIDE operator
The description for the new 'inside' operator (LRM-16) defines
'range_list_or_array' as below:
inside_expression ::= expression inside range_list_or_array
range_list_or_array ::=
variable_identifier
| { value_range { , value_range } }
range_list_or_array is a comma-separated list of integral expressions and
ranges. Value ranges are specified in ascending order with a low and high
bound, enclosed by square braces [ ], and separated by a colon ( : ), as in
[low_bound:high_bound]. Ranges include all of the integer elements between
the bounds. If the bound to the left of the colon is greater than the bound
to the right the range is empty and contains no values.
The text only covers the range_list part and not the array part. It should
be something like:
The set membership (range_list_or_array) is defined by a comma-separated
list of integral expressions and ranges or an array of integral elements
(variable_identifier). Value ranges are specified in ascending order with a
low and high bound, enclosed by square braces [ ], and separated by a colon
( : ), as in [low_bound:high_bound]. Ranges include all of the integer
elements between the bounds. If the bound to the left of the colon is
greater than the bound to the right the range is empty and contains no
values. Each element of an array is included in the set."
[Arturo] Your changes do clarify the meaning, but I think your
generalization below is even better.
Is the array restricted to be a single dimensioned array?
[Arturo] One dimension was certainly the intent.
I think allowing multi-dimensional arrays will require
additional rules to determine how the array is used. For example:
bit [10:1] a [20:1] ;
Does "x inside a" mean each 10 bit value, or each individual
bit. The more packed dimensions, the more complex.
Also:
Why can't the array reference be a hierarchical reference, or a slice? Why
not allow the membership
set to be defined by an array and a range, or multiple arrays? It would be
more general to define the
set membership as below:
Change:
inside_expression ::= expression inside range_list_or_array
range_list_or_array ::=
variable_identifier
| { value_range { , value_range } }
value_range ::=
expression
| [ expression : expression ]
To:
inside_expression ::= expression inside set_membership
set_membership ::=
expression_or_range
| { expression_or_range { , expression_or_range} }
expression_or_range ::=
expression
| [ expression : expression ]
Notes: a) if an expression references an array, each element of the
array in included in the set.
b) the { } syntax is not needed - set membership could be a
simple list.
[Arturo] Allowing set_membership to include any number of (one dimensional)
arrays or expressions is a very nice generalization to the semantics of this
operator. I propose that we vote this enhancement in. However, I don't like
the syntactic change (removing the braces), for a number of reasons:
1) It would make the inside operator inconsistent with the dist operator
(essentially set membership with distribution).
2) Most statements in verilog include some sort of delineation around
the various operand, not just a semicolon.
For example, task calls don't need parenthesis: foo( a, b, c );
instead of foo a, b, c;
3) Unpacked array expressins also use braces, and set_membership is a
certainly a form of unpacked array expression.
I believe the syntax is just:
inside_expression ::= expression inside range_list_or_array
range_list_or_array ::= { value_range { , value_range } }
And a sematic restiction that limits value range to either simple values or
one-dimensional arrays.
Regards
Ray Ryan
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