# Using Operators in Swift

This chapter is from the book

## Binary Operators

Binary operators are operators that affect operands, which are the values on either side of the operator. For example, take a + b. In this expression, a and b are operands, and + is the operator. All Binary operators are infix, meaning they are in between two operands.

### Standard Arithmetic Operators

Swift provides the four standard arithmetic operators that are binary operators for all numeric types, which are addition (+), subtraction (-), division (/), and multiplication (*). To use these operators in code, you use them exactly the way you would write them in a math equation:

```let a = 5 + 5 // a equals 10
let b = 3 - 2 // b equals 1
let c = 8.0 / 5.0 // c equals 1.6
let d = 4 * 4 // d equals 16```

### Remainder Operator

Swift includes a remainder operator, annotated by the % sign. In other languages, this operator is called the modulo operator, which has slightly different behavior. Swift calculates the remainder operator by figuring out how many times b evenly divides a, and returns the remainder. In other words, a = (b * multiplier) + remainder, with multiplier being the largest number b could multiply against to not produce a value higher than a.

In languages like C and Objective-C, the modulo operator behaved similarly, but unlike Swift, it could not perform against floating-point numbers; you would get a compiler error as the modulo operator cannot take floating-point numbers as its operands. This is another reason that Swift’s remainder operator is truly a remainder operator, because Swift gives the remainder of what is left over from a - (b * multiplier). Listing 3.1 displays the modulo operator in C.

#### LISTING 3.1 Modulo Operator in C and Objective-C

```int a = 8;
int b = 6;
int c = a % b; // returns 2, as expected
int d = -8;
int e = d % b; // returns -2, as expected```

In C and Objective-C, the modulo operator is pretty straightforward, as long as you’re providing integers. Listing 3.2 displays the remainder operator in Swift, which not only works with integers like C, but can also operate on Double types.

#### LISTING 3.2 Remainder Operator in Swift

```let a = 8
let b = 6
let c = a % b // returns 2, just as in C
let d = 8.0
let e = 2.5
let f = d % e // returns 0.5, Swift allows remainders for Double types```

### The Assignment Operator

There is just one assignment operator in Swift, as in other languages, and that is the equal sign (=). The assignment operator takes the calculated or literal value on the right side of the equal sign and assigns it to the variable or constant on the left side of the equal sign. We have seen the assignment operator many times throughout this book already, and every single line in Listing 3.1 and Listing 3.2 utilizes the assignment operator.

### Compound Assignment Operators

Compound assignment operators in Swift utilize the previously mentioned assignment operator (=), coupled with another operator, to perform a combined effect. Table 3.1 details each operator, what code it is short for, and a description.

#### TABLE 3.1 Compound Assignment Operators

 Operator Example Longer Expression Description += a += b a = a + b Add, then assign -= a -= b a = a - b Subtract, then assign *= a *= b a = a * b Multiply, then assign /= a /= b a = a / b Divide, then assign %= a %= b a = a % b Compute remainder, then assign

Table 3.1 shows some of the basic compound operators. However, there are many more compound operators, all of which are more advanced than the scope of this book, such as bitwise and logical compound operations. For more information on these operators, see the chapter on expressions in The Swift Programming Language, Apple, 2015.

### Comparison Operators

Comparison operators in Swift are similar to those of other programming languages. Each one returns a Boolean value describing whether the expression was true or false. Table 3.2 lists the basic comparison operators.

#### TABLE 3.2 Comparison Operators

 Operator Example Description > a > b Returns true if a is greater than b, else false. < a < b Returns true if a is less than b, else false. >= a >= b Returns true if a is greater than or equal to b, else false. <= a <= b Returns true if a is less than or equal to b, else false. == a == b Returns true if a is equal to b, else false. != a != b Returns true if a is not equal to b, else false.

As with comparison operators, there are other advanced operators. We cannot discuss them all in this book, but we cover two more of them in Hour 10, “Learning About Structs and Classes.”

### Range Operators

Range operators in Swift are denoted by two dots and a left angle bracket (..<) or three dots (...) depending on what type of range you need. There are two types of range operators: half-closed range operators and closed range operators.

A half-closed range operator uses two dots and a left angle bracket to indicate a range of integers from its left-hand operand up to but not including the right-hand operand. The expression 1..<5 defines a range of four integers, 1 through 4, but not including 5. You can also use variables or constants with range operators, such as 1..<a. The half-closed operator is called as such because its range contains its initial value but not the final value.

A closed range operator uses three dots to indicate a range of integers from its left-hand operand up to and including the right-hand operand. The expression -2...2 defines a range of five integers, from -2 to +2. The closed range operator can also use variables or constants as operands, such as a...b. The closed range operator is called closed range because the range is closed on each end by including both operands.

Both half-closed range operators and closed range operators are useful in iterative expressions. Closed range operators are good for ranges where you want both the first and last values of the range to be included. Half-closed range operators are especially good for zero-based lists such as arrays, where the index of the first element is 0, followed by 1, then 2, and so on. Arrays are discussed in more detail in Hour 4, “Working with Collection Types.” Consider the code in Listing 3.3—it illustrates the differences in the two range operators.

#### LISTING 3.3 Different Range Operators

```for a in 1...5 {
print(a)
}
//This closed range prints the following:
//1
//2
//3
//4
//5
let arrayLength = 3
for b in 0..<arrayLength {
print(b)
}
//This half-closed range prints the following:
//0
//1
//2```

### Logical Operators

Swift provides three logical operators, AND (&&), OR(||), and NOT (!). These operators are called logical operators because they evaluate upon and return Boolean value types based on logic. The three logical operators compare the bits inside their given operands, perform the operation against them, and then return the result. These three operators are similar to those you would find in other languages, but we discuss them here if you’re not familiar.

#### Logical AND Operator

The logical AND operator, sometimes referred to as just AND, performs a logical AND operation against both operands and returns the result. Let’s illustrate how AND operates and comes up with a return value. Look at the truth table in Table 3.3.

#### TABLE 3.3 Logical AND Operator Truth Table

 Operand 1 Operand 2 AND Result True True True True False False False True False False False False

Let’s say you’re comparing two Boolean values, a and b, in the following code sample:

```let a = true
let b = false
let c = a && b```

What value does c have? You’re right; c is false. The AND operator is useful when every value in a certain set of conditions needs to be met first before executing an expression or set of expressions. For example, the following code snippet illustrates what use of the AND operator looks like if you were to try to get access to a device’s motion data:

```if CMPedometer.isStepCountingAvailable() && userAcceptedUseOfMotionProcessor {
/* it's now ok to get step data */
} else {
print("cannot get step data")
}```

If step counting is not available (known by the Boolean return value of CMPedometer.isStepCountingAvailable()) or if the user has explicitly stated it’s not okay for us to have access to the device’s motion coprocessor, then we cannot count the user’s steps.

#### Logical OR Operator

The logical OR operator is similar in syntax to the AND operator but behaves slightly differently. The OR operator evaluates two operands and decides whether either one is true or not, no matter which one, and then returns its result. The truth table in Table 3.4 details the OR operator’s behavior.

#### TABLE 3.4 Logical OR Operator Truth Table

 Operand 1 Operand 2 OR Result True True True True False True False True True False False False

The OR operator returns true if either operand in the expression is true. Let’s take another look at a simple code snippet to illustrate OR:

```let a = true
let b = false
let c = a || b```

What is the value of c? Again, you’re right; the value is true. A more realistic example might look something like this:

```if userHasCellularConnectivity || userHasWifiConnectivity {
// assume user has an internet connection, start talking to web service
} else {
// warn user to enable connectivity hardware
}```

In the previous example, if either of the two operands (userHasCellularConnectivity or userHasWifiConnectivity) is true, then the first block of code executes. If neither operand is true, the second block of code executes. We cover conditionals with if statements in Hour 5.

#### Logical NOT Operator

The last logical operator, NOT, as mentioned earlier, simply inverts the value of a Boolean variable or constant. Although not a binary operator, NOT is listed here in the logical operators section for completeness. For example, see Table 3.5 for the truth table illustrating the values resulting from the NOT operator.

#### TABLE 3.5 Logical NOT Operator Truth Table

 Operand NOT Result True False False True

#### Combining Logical Operators

Logical operators can be combined into larger expressions where multiple lines of logic may be required. The expression a && b || !c combines all three logical operators and can be read as “a and b must be true, or not c”. While not required, you can insert parentheses to explicitly state the order of operations you want in your code, such as (a && b) || (!(c && d)).

### InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

## Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

## Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

### Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

### Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

### Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

### Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

### Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

### Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

## Other Collection and Use of Information

### Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

### Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

### Do Not Track

This site currently does not respond to Do Not Track signals.

## Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

## Children

This site is not directed to children under the age of 13.

## Marketing

Pearson may send or direct marketing communications to users, provided that

• Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
• Such marketing is consistent with applicable law and Pearson's legal obligations.
• Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
• Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

## Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

## Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

## Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

## Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

## Sharing and Disclosure

Pearson may disclose personal information, as follows:

• As required by law.
• With the consent of the individual (or their parent, if the individual is a minor)
• In response to a subpoena, court order or legal process, to the extent permitted or required by law
• To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
• In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
• To investigate or address actual or suspected fraud or other illegal activities
• To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
• To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
• To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.