As we saw in the truth table, a Boolean expression that uses logical operators can be as simple as evaluating two boolean values:
bool answer = true && false; // evaluates to False
In this case, we’re saying that
answer is equal to the evaluation of
false. According to the truth table,
answer will return False.
But more often, Boolean expressions are extremely complex. Rather than determining if one relationship is true or false, we can evaluate several expressions by connecting them with logical operators and then determining the validity of the overall expression.
bool answer = (9 < 3) || (100 < 45); // evaluates to False bool another = ((3439 > 40) && (1 < 3)) || answer; // evaluates to True
We can use logical values to start chaining logical statements.
Let’s start by finding the value of
First, the computer will evaluate each comparison statement:
bool answer = (9 < 3) || (100 < 45)
Both of these statements evaluate to false:
bool answer = false || false
Since both statements evaluate to false and we’re using an OR operator, the overall expression will return false:
bool answer = false
Now we can start evaluating the value of
Again, we’ll start by evaluating the comparison statements:
bool another = ((3439 > 40) && (1 < 3)) || answer
Both statements evaluate to true:
bool another = (true && true) || answer
Since both statements evaluate to true and we’re using an AND operator, the overall expression returns true:
bool another = true || answer
Since we already know that
answer is false and we’re evaluating it with a true value using an OR operator
another, it will return true:
bool another = true.
You and your friend are planning a trip together and are trying to decide where to go. You each have specific criteria that it needs to fulfill. You want it to have a beach and city, whereas your friend wants beach or hiking. Your current pick is Barcelona, which is a city that has a beach. Will both you and your friend be happy?
bool variable named
yourNeeds. Write a logical comparison that captures your criteria.
bool variable named
friendNeeds. Write a logical comparison that captures their criteria.
Write a logical comparison that compares
friendNeeds and save it to
tripDecision to the console. Will you agree on Barcelona? You should only go if it satisfies both your needs and your friend’s needs.
What about Portbou, a smaller town (not a city) with a beach but no hiking?