[sv-ec] Reduction method on empty array

Some dynamic array types can be empty (have no elements).  What should be
the result of an array reduction method applied to such an array?

Possible answers:

1. The "identity" value for the operation (e.g. 0 for sum, but 1 for product).
This would be the most natural degenerate value.  The result for an N-element
array is the same as combining the Nth element with the result for an
(N-1)-element array.  Using the identity value for 0 would ensure that this
remained true for N=1 also.

2. The "default" or "out-of-range" value for the element type (or type of
the 'with' expression, if any).  This would be natural if this is considered
an "out-of-range" situation.  As a slight alternative, it could be the result
of initializing the accumulation with the array[0] element.  This would be
the same as the "out-of-range" value unless a 'with' clause was used that
evaluated to a different value.

3. This could be a run-time error.

Steven Sharp
sharp@cadence.com


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