第2个回答 2021-10-27
Specifying Systems 2002.Leslie Lamport
F G F ⇒G
true true true
true false false
false true true
false false true
The formula F ⇒ G asserts that F implies G —that is, F ⇒ G equals true
iff the statement “F implies G ” is true. People often find the definition of
⇒ confusing. They don’t understand why false ⇒true and false ⇒false
should equal true. The explanation is simple. We expect that if n is greater
than 3, then it should be greater than 1, so n > 3 should imply n > 1. Therefore,
the formula (n > 3) ⇒(n > 1) should equal true. Substituting 4, 2, and 0 for
n in this formula explains why F ⇒ G means F implies G or, equivalently, if
F then G
Q.E.D