RE: [sv-bc] sign/width casting semantics

________________________________

From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On
Behalf Of Feldman, Yulik
Sent: Thursday, January 31, 2008 3:14 PM
To: Greg Jaxon; danielm
Cc: Brad Pierce; sv-bc
Subject: RE: [sv-bc] sign/width casting semantics

 

1.	6.24.1 says "When changing the signing, the type of the
expression to be cast shall pass through unchanged, except for the
signing", but it doesn't elaborate which direction of the "pass" is
affected, the upward, the downward, or both. 

 

[Yulik] After reading this sentence again, I now see that it says
"expression to be cast", so the intention should be for upward direction
only. This leaves the question of behavior for downward direction open.
However, taking into account that "the cast shall return the value that
a variable of the casting type would hold after being assigned the
expression" and 11.7.3, this leaves as with the only sensible option for
the downward direction is that the signedness of the context should not
be propagated in that direction. 

 

So, seemingly, the main open question is whether the operand of
signed'() is context- or self-determined (i.e. whether the size should
be propagated or not). I agree with recent Shalom's comments that there
are not many reasons to treat it as context-determined.


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