Re: [sv-bc] FW: interpreation of priority if-else or case statement

I think that Antara Ghosh is interpreting the LRM correctly.

I also think that the 'priority' and 'unique' qualifiers are not a
good design.

The normal, and traditional, reading of an unqualified if-then-else or
case is prioritized anyway, i.e., sequential from top-to-bottom, and
the conditions need not be mutually exclusive.

The two extra properties of interest in conditionals are uniqueness
(mutually-exclusiveness of conditions) and exhaustiveness (all possibilities
are covered).  I think it would have been much clearer to have two qualifiers
saying exactly that:

   'unique'     : asserting mutually-exclusiveness (but not necessarily exhaustiveness)
   'exhaustive' : asserting exhaustiveness (but not necessarily mutually-exclusiveness)

(of course, an 'else' or 'default' clause makes things exhaustive).

Currently,

   'unique'     : asserts mutually-exclusiveness
                  and exhaustiveness (no way to say 'mutually-exclusive but not exhaustive?)


   'priority'   : asserts sequentiality(which is redundant)
                  and exhaustiveness which is not apparent from the choice of word 'priority')

Nikhil


Maidment, Matthew R wrote:
>>From: Antara Ghosh <antarag@interrasystems.com>
>>To: sv-bc@server.eda.org
>>Subject: interpreation of priority if-else or case statement
>>
>>Hello,
>>
>>What is the difference between the behavior of priority if-else/case 
>>statement and normal (without unique or priority attribute) if-else 
>>statement?
>>
>>LRM states "A priority if indicates that a series of if ... 
>>else ... if 
>>conditions shall be evaluated in the order listed." But that is the 
>>inherent behavior of an if-else if statements. The only difference 
>>between normal if and priority if seems to be the fact that the later 
>>errors out if there is a condition which is not present in 
>>if-else ladder.
>>Please let me know if I am missing something.
>>
>>Thanks
>>Antara Ghosh
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