RE: [sv-bc] confusion in determining the type of an self determined binary expression during evalution of type operator

 

 

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From: Bresticker, Shalom 
Sent: Sunday, October 21, 2007 12:20 PM
To: Feldman, Yulik
Cc: 'sv-bc@server.eda.org'
Subject: RE: [sv-bc] confusion in determining the type of an self
determined binary expression during evalution of type operator

 

Maybe it would be better, instead of trying to list all the
possibilities (though Mantis 2072 contains an attempt to do so), to just
say generally that the LHS of a procedural assignment can be a variable,
select thereof, or a concatenation or assignment pattern of such. And
the LHS of a continuous assignment can be a net or variable, constant
select thereof, or a concatenation or assignment pattern thereof. (Are
those statements correct?)

[Yulik] Sounds good

 

I don't think it is correct to 'add "array slice" at almost every place
where "bit-select" or "part-select" is used'. The reason is that many,
if not most, of those places are where a singular operand is required,
whereas an array slice is an aggregate.

[Yulik] Note that there is a difference between of what kind of type a
select can be applied on, and the kind of type than the select may
return. If singular operand is required, you may still be allowed to use
a select on complex data type, just a kind of select that returns a
singular type. "bit-select" and "part-select" restrict the type they are
applied to, and thus are often not enough to describe all valid cases.

 

One of the reasons for the attempts to specify precisely what constructs
are allowed is that not every type of select is allowed everywhere. For
example, bit-selects are allowed on packed structures, but not on
unpacked structures. 

[Yulik] I'm not sure this is a good example. What makes the difference
here is the packedness of the structure, not the kind of select. In the
description of packed structures, you just need to say that they may be
treated as one-dimensional arrays (which is already said). Then, you
don't need to elaborate what kinds of selects are allowed on those
arrays; you may just say selects. 

 

I'm really having a difficult time finding a place in LRM where saying
just a general "select" would not be correct or precise enough. In most
cases the usage is already limited by the types the "operand" of the
select may get, so there is no need to restrict this usage again by
elaborating the specific kind of select allowed.

 

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