PCF 8574 example from nopnop

Hello sir Thank you so much for your help! In your topic PCF8574 you give as an example a link to a Japanese author "nopnop". It's very interesting, but I'm a novice, and I don't understand the meaning of this line of code: Could you explain to me the meaning of the two ::? PCF8574 :: DigitalInput val = pcf8574.digitalReadAll (); Slowly please :-) like a child I'm just starting out, and it's been fifteen days that I browse the websites, and in fact I'm going from one problem to another. the syntax of C is difficult. Thank you anyway and long life to your blog