the code is from the shiftou() function if that helps.
The second variable of a digitalWrite function is defined as a Boolean, no?
2) C doesn't have a "boolean" type.
C doesn't have a "boolean" type.
typedef uint8_t boolean;
boolean myval = 33;
and the compiler won't complain (and myval will actually contain 33, rather than becoming just "true.")
So the use "!!" is neither correct nor necessary.)