I am reading a book called "The Haskell Road to Logic, Maths and Programming"
A question in the book is: "How many truth tables are there for 2-letter formula's"
The answer in the answer sheet is:
"A two-letter formula has a truth table with four rows. The value at every row can be either t of f, so there
are 2^4 = 16
truth tables altogether."
Now I don't understand, how a 2 letter formula, can have 16 truth tables?
Let's say P ⇒ Q
It will look like:
P Q (P⇒Q)
T T T
T F F
F T T
F F T
Now how can this have 16 tables? It looks like one table to me.