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Understanding Logic in C#
Logical Operators

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 true AND 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 answer.

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 another. 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.

Instructions

1.

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?

Create a bool variable named yourNeeds. Write a logical comparison that captures your criteria.

2.

Create a bool variable named friendNeeds. Write a logical comparison that captures their criteria.

3.

Write a logical comparison that compares yourNeeds and friendNeeds and save it to tripDecision.

Print 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?

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