I thought I pretty much knew everything about the standard functions in
Excel, but this thread has something I've never encountered. What does
"--" before the function do?

Ivan Raiminius wrote:
Hi Kris,

I need to know how many are in A but don't have anything in B:
=SUMPRODUCT(--ISNUMBER(A1:A4),--ISBLANK(B1:B4))

How many are in C but don't have anything in A or D:
=SUMPRODUCT(--ISNUMBER(C1:C4),--ISBLANK(A1:A4),--ISBLANK(D1:D4))

Regards,
Ivan