RE: [sv-bc] part selects on arbitrary expressions

[Shalom]
From those points of view, using concatenations, i.e., allowing 
bit-selects and part-selects of concatenations, is much less 
ambiguous. It is only a partial solution, in that it would 
only deal with 1-D arrays
[Yulik] 
...For me, a solution that will not account for complex 
data types will not be really a solution.

As Mike McNamara has wisely suggested, you could
reasonably use concatenation braces {} to imply flattening
of a self-determined expression so that its outermost subscript
range is of the form [N-1:0], although it's important to note
that this would represent a subtle change of the data type of
the expression.  But Yulik seems to want to similarly flatten
*all* subscript ranges, right the way down through the whole
structure of the expression.  

I find this completely unacceptable unless we have some new 
syntax to do this subscript-normalisation explicitly.  For
example, we could borrow the style of bitstream operators
and do this (only an example, I'm not advocating this
specific syntax):

  {[]{ expression }}

where the [] "operator" is taken to mean "create a primary 
having the same data type as expression, but with all its
subscript ranges normalised to [N-1:0]".  You could then
do arbitrary subscripting and selection like this...

  typedef struct 
    logic [20:21] p[5:7];
    byte q;
  Thing [50:48];

  function Thing func(...) ... endfunction

Given those declarations, the expression

  {[]{ func(...) }} [2].p[2][1]

would now reliably represent the extreme leftmost
bit of the struct returned by func().

Without some completely new syntax, slicing and
selection on expressions is always going to be 
a mess and it must be rejected.
--
Jonathan Bromley, Consultant

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