Add16 and input bits seem inverted, why?

[wetFence]

I don't understand how the Add16 inputs work.

In my mind these two things are equivalent:

b=0000000000000001

and

b[15]=true

Am I correct?

So if I do

Add16(a=false, b[15]=true, out=out);

then I would expect the result to be

0000000000000001

but instead it is

1000000000000000

To get the right result, I have to do

b[0]=true

Why the inversion?

I know my Add16 is valid because it passes the tests, I'm trying to implement Inc16 from Add16 chips.

[ybakos]

The 16 bits are indexed right-to-left.

When bit 15 is a 1, and the rest are 0, you have 1000000000000000.

[cadet1620]

The rationale for numbering hardware bits from right to left is so that bit n is the 2ⁿ-weighted bit of the binary number on the bus.

--Mark

[wetFence]

Thanks to both of you, that makes sense now.