Implication (==>, <==, and <==>)

The operator P ==> Q, read P implies Q, is equivalent to !P || Q.

This can also be written backwards: Q <== P is equivalent to P ==> Q.

Finally, P <==> Q is equivalent to P == Q. It is sometimes useful for readability, and because <==> has the same syntactic precedence as ==> rather than the precedence of ==.