RE MCP23017 and interrupts and Adafruit MCP23017 library

Not all that intuitive way of implementing it in the wire library from where I am sitting but OK, now it makes sense.

You don't need to quote my entire message, which immediately precedes yours. That's just clutter. I deleted it.

Or is it a typo and should read as follows?

As the datasheet says:

The PortA registers are identical to the PortB registers, therefore, they will be referred to without differentiating between the port designation (i.e., they will not have the “A” or “B” designator assigned) in the register tables.