I was reading the arduino sample. Unrebounce. There is a statement.
int i = LOW
I = ! i
What does it do?
What does it do?
Generate a compiler error.
You code fragment has numerous problems:
int i = LOW // No semicolon at the end of the statement line
I = ! i // Variable I not defined, missing semicolon at end of statement line
If you fix the errors and add a few Serial.print() statements, you should be able to figure out what the expression does.
Nevertheless,
In C (and C++), the conversion from integer to boolean is that integer 0 is boolean false, anything else is boolean true. The conversion from boolean back to integer is that false becomes 0, true becomes 1. So !x, where x is an integer, turns zero into 1, and any nonzero value into 0.