The unary minus (-) operator negates values (positive to negative,
negative to positive). Using two in a row restores the sign.

As with any math operator, XL tries to coerce operands to numeric
form if it can. With TRUE/FALSE, XL coerces them to 1/0,
respectively, so

--TRUE == --(1) == -(-1) == 1

--FALSE == --(0) == -(-0) == 0

You could accomplish the same thing with

TRUE + 0 == (1) + 0 == 1

but double unary minus seems to be a bit faster and has a higher
precedence.

In article ,
"Todd S" wrote:

I've recently been introduced to the following formula
through Newsgroups:
=SUMPRODUCT(--(Sheet1!$B$2:$B$9000=1),--(Sheet1!
$C$2:$C$9000=14))

It works for my needs, however, I'm trying to understand
it for other applications.

What do the -- operators do? I've never seen them before
and can't find a reference.