Subject: Re: Auto-increment proposal with example
From: Karen Pieper (Karen.Pieper@synopsys.com)
Date: Wed Jan 08 2003 - 18:40:56 PST
Hi, all,
Paul's comments are the only ones I've received on the proposal I
originally sent. His comments
were on the original unmodified paragraph that I was using to indicate
where to add the new
paragraph. I will add his comments as a new issue for us to track. Since
there were no changes
to the proposed new wording, and there exists a second, we can vote on this
proposal. If there
are no comments on the new wording (not the existing wording) by Wednesday,
January 15
at 6:00pm PST, the proposal will pass.
Thanks,
Karen
Increment decrement proposal:
In Section 7.3:
REPLACE: SystemVerilog also includes the C incrementor and decrementor
operators ++i, --i, i++ and i-- (provided there is no timing control). These
can be used in expressions without parentheses. These increment and
decrement operations behave as blocking assignments.
WITH: SystemVerilog also includes the C incrementor and decrementor
operators ++i, --i, i++ and i-- (provided there is no timing control). These
can be used in expressions without parentheses. These increment or
decrement operations behave as blocking assignments.
<new paragraph>
The ordering of assignment operations relative to any other operation
within an
expression is undefined. An implementation may warn whenever a variable is
both
written and read-or-written within an integral expression or in other contexts
where an implementation cannot guarantee order of evaluation. Consider the
following
example:
i = 10;
j = i++ + (i = i - 1);
After execution, the value of j can be 18, 19, or 20 depending upon the
relative ordering
of the increment and the assignment statements.
At 05:33 PM 1/6/03 -0800, Paul B. Graham wrote:
> > WITH: SystemVerilog also includes the C incrementor and decrementor
> > operators ++i, --i, i++ and i-- (provided there is no timing control).
> These
> > can be used in expressions without parentheses. These increment or
> > decrement operations behave as blocking assignments.
>
>Why the difference between:
>
> ... include the C incrementor and decrementor operators ...
>
>and
>
> ... These increment or decrement operations ...
>
>Why not use the same wording?
>
>Does "provided there is no timing control" mean "provided there is no timing
>control in the design"? Or does it mean that inc/dec cannot be used within
>a delay expression?
>
>Why say they can be "used in expressions without parentheses"? Does this
>mean they cannot be used in expressions with parentheses? For instance, are
>
> x = (i++);
> y = i++ + (j);
>
>illegal? Is the intent to say that inc/dec can only be applied to an
>lvalue?
>
>Paul
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