By defining the function to return void, you CANNOT return a value. If you want to return a value, then you wouldn't use a function returning void.
If you want to return LOW or HIGH then have the function return int.
int print() {
if(intPressure != 0)
{
Serial.println("HIGH");
tweet = HIGH;
}
else
{
Serial.println("LOW");
tweet = LOW;
}
return tweet;
}
And then to use it in the loop function you'd have to assign that return value to something or use it somewhere it is useful. Like:
int someVariableName = print();
or even:
if(print()){
// code for when tweet was HIGH
}
else {
//code for when tweet was LOW
}