Swift Language Reference

Question 1

What is Lexical Structure?

Answer 1

Describes what sequence of characters form valid tokens of the language.

Question 2

What is a token?

Answer 2

Consists of an identifier, keyword, punctuation, literal, or operator.

Question 3

What is a valid token?

Answer 3

Form the lowest-level building blocks of the language and are used to describe the rest of the language

Question 4

How are tokens are generated?

Answer 4

Generated from the characters of a Swift source file by considering the longest possible substring from the input text, within the constraints of the grammar. This behavior is referred to as longest match or maximal munch.

Question 5

What is an Identifier?

Answer 5

Uppercase or lowercase letter A through Z, an underscore (_), a noncombining alphanumeric Unicode character in the Basic Multilingual Plane, or a character outside the Basic Multilingual Plane that isn’t in a Private Use Area. After the first character, digits and combining Unicode characters are also allowed.

Question 6

How to use a reserved word as an identifier?

Answer 6

put a backtick (`) before and after it.
For example, class is not a valid identifier, but `class` is valid. The backticks aren’t considered part of the identifier; `x` and x have the same meaning.

Question 7

how to refer to parameters inside a closure with no explicit parameter names?

Answer 7

$0, $1, $2, and so on.

Question 8

Keywords used in declarations:

Answer 8

associatedtype, class, deinit, enum, extension, fileprivate, func, import, init, inout, internal, let, open, operator, private, protocol, public, static, struct, subscript, typealias, and var.

Question 9

Keywords used in statements:

Answer 9

break, case, continue, default, defer, do, else, fallthrough, for, guard, if, in, repeat, return, switch, where, and while.

Question 10

Keywords used in expressions and types:

Answer 10

as, Any, catch, false, is, nil, rethrows, super, self, Self, throw, throws, true, and try.

Question 11

Keywords used in patterns:

Answer 11

_.

Question 12

Keywords that begin with a number sign (#):

Answer 12

available, #colorLiteral, #column, #else, #elseif, #endif, #error, #file, #fileLiteral, #function, #if, #imageLiteral, #line, #selector, #sourceLocation, and #warning.

Question 13

Keywords reserved in particular contexts:

Answer 13

associativity, convenience, dynamic, didSet, final, get, infix, indirect, lazy, left, mutating, none, nonmutating, optional, override, postfix, precedence, prefix, Protocol, required, right, set, Type, unowned, weak, and willSet. Outside the context in which they appear in the grammar, they can be used as identifiers.

Question 14

The following tokens are reserved as punctuation and can’t be used as custom operators:

Answer 14

(, ), {, }, [, ], ., ,, :, ;, =, @, #, & (as a prefix operator), ->, `, ?, and ! (as a postfix operator).

Question 15

What is a Literal?

Answer 15

A literal is the source code representation of a value of a type, such as a number or string.

The following are examples of literals:

42 // Integer literal
3.14159 // Floating-point literal
“Hello, world!” // String literal
true // Boolean literal

Question 16

To which protocols does an annotation for a literal value have to conform in order to be inferred?

Answer 16

Swift standard library protocols:
ExpressibleByIntegerLiteral for integer literals, ExpressibleByFloatLiteral for floating-point literals, ExpressibleByStringLiteral for string literals, ExpressibleByBooleanLiteral for Boolean literals, ExpressibleByUnicodeScalarLiteral for string literals that contain only a single Unicode scalar, and ExpressibleByExtendedGraphemeClusterLiteral for string literals that contain only a single extended grapheme cluster.

For example, Int8 conforms to the ExpressibleByIntegerLiteral protocol, and therefore it can be used in the type annotation for the integer literal 42 in the declaration let x: Int8 = 42.

Question 17

What are Integer Literals?

Answer 17

Integer literals represent integer values of unspecified precision.

Question 18

What are the integer literals types?

Answer 18

Decimal 0-9,
Binary begin with 0b from 0-1, 
Octal begin with 0o from 0-7, 
Hexadecimal begin with 0x from 0-9 A-F or a-f.
Negative -(0-9)

Question 19

What are underscores (_) used for in integers?

Answer 19

readability:
1_0 is equal to 10
001 is equal to 1
00_1 is equal to 1

Question 20

What are the Floating-Point Literals?

Answer 20

Floating-point literals represent floating-point values of unspecified precision.

Question 21

What is the default inferred type of a floating-point literal?

Answer 21

Unless otherwise specified, the default inferred type of a floating-point literal is the Swift standard library type Double

Question 22

How many bits is a Double floating-point number?

Answer 22

64-bit

Question 23

How many bits is a Float floating-point number?

Answer 23

32-bit

Question 24

How can String literals be declared?

Answer 24

single-line = “These are the same.”
multi-line = “””
These are the same.
“””

Question 25

What are the String scape sequences?

Answer 25

Basically using a backlash (\)
Null character (\0)
Backslash (\\)
Horizontal tab (\t)
Line feed (\n)
Carriage return (\r)
Double quotation mark (\")
Single quotation mark (\')
Unicode scalar (\u{n}), where n is a hexadecimal number that has one to eight digits