The importance of the double unary minuses is simply an efficient way to
convert a boolean array to a numeric array that SUMPRODUCT will work
with (it will treat booleans as 0).

Multiplying the arrays first before passing the result to SUMPRODUCT
also coerces the arrays to numeric, though at a small loss of efficiency
(presumably SUMPRODUCT's internal array multiplication is faster than
multiplying the arrays first, then passing that array).

SUMPRODUCT cannot multiply arrays of different dimensions, so if you
want to sum such a result, you have to first do the multiplication, then
send the result to SUMPRODUCT().




In article ,
"vipa2000" wrote:

Do i need to be worried about the loss of the --
prefixes? I have read a number of articles on the importance of these.