A double minus is also known as a double urnary.

In this formula: =SUMPRODUCT(--(A1:A10 & D1:D10="1A"))

this section: (A1:A10 & D1:D10="1A")
returns a series of boolean (fancy word for: TRUE/FALSE) values
....which are not numeric to Excel.

When an arithmetic operator (+,-,*,/) is applied to a boolean value,
Excel converts TRUE to 1 and FALSE to 0.

The standard convention is to use
the Double-Minus (--) to convert the values.
It works this way:
TRUE=TRUE
-TRUE = -1
--TRUE = 1

FALSE = FALSE
-FALSE = 0
--FALSE = 0

Now, you could easily use 1*TRUE, but the Dbl-Minus indicates to
knowledgable users that you are forcing a conversion and not
trying to calculate something.

So, In the formula, the TRUE/FALSE values are converted to 1's and 0's
by the "--" and the SUMPRODUCT calculates the total.

- explanation contribution thanks to Ron Coderre from a previous post


--

"Minitman" wrote in message
...
Greetings,

What does the double minus (--)sign in front of a command signify?

-Minitman