[sv-ec] Mantis 1707 - bitstream operators

hi SV-EC,

I'm on the point of posting a reference algorithm for the
bitstream operators, as promised.  However, doing the work
has prompted a question:  Why the asymmetry between the
two directions?

Consider the bitstring "abcdef" (where each character 
symbolically represents a single bit).  Now,

  { << { abcdef } } == fedcba   // bit reversal
  { >> { abcdef } } == abcdef   // simple packing

So far, so good.  But...

  { << 3 { abcdef } } == defabc   // reverse order of slices,
                                  // keep order within each slice
  { >> 3 { abcdef } } == abcdef   // simple packing

In fact, the [slice_size] operand has absolutely no
effect for >>.  Was this always the intent?  Surely 
it would be more symmetrical, reasonable and useful
for >> likewise to respect the slice size...

  { >> 3 { abcdef } } == cbafed   // keep order of slices,
                                  // reverse order within each slice

Alternatively, if the [slice_size] operand is ignored by >>,
would it not be a smart move to forbid its presence?

Thanks
-- 
Jonathan Bromley, Consultant

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