Expressions

Question 1

What kinds of expressions are there in Swift?

Answer 1

In Swift, there are four kinds of expressions: prefix expressions, binary expressions, primary expressions, and postfix expressions.

Prefix and binary expressions let you apply operators to smaller expressions.

Primary expressions are conceptually the simplest kind of expression, and they provide a way to access values.

Postfix expressions, like prefix and binary expressions, let you build up more complex expressions using postfixes such as function calls and member access.

Question 2

What does evaluating an expression do?

Answer 2

Evaluating an expression returns a value, causes a side effect, or both.

Question 3

Name the prefix operators defined by the Swift standard library.

Answer 3

\++ Increment
-- Decrement
! Logical NOT
~ Bitwise NOT
\+ Unary plus
- Unary minus

Question 4

What other prefix operator is defined by the Swift language?

Answer 4

In addition to the standard library operators listed above, you use & immediately before the name of a variable that’s being passed as an in-out argument to a function call expression.

Question 5

What exponentiative binary operators does the Swift standard library provide?

Answer 5

&laquo_space;Bitwise left shift
» Bitwise right shift

(No associativity, precedence level 160)

Question 6

What multiplicative binary operators does the Swift standard library provide?

Answer 6

* Multiply
/ Divide
% Remainder
&* Multiply, ignoring overflow
&/ Divide, ignoring overflow
&% Remainder, ignoring overflow
& Bitwise AND

(Left associative, precedence level 150)

Question 7

What additive binary operators does the Swift standard library provide?

Answer 7

\+ Add
- Subtract
&+ Add with overflow
&- Subtract with overflow
| Bitwise OR
^ Bitwise XOR

(Left associative, precedence level 140)

Question 8

What range binary operators does the Swift standard library provide?

Answer 8

.. Half-closed range
… Closed range

(No associativity, precedence level 135)

Question 9

What cast binary operators does the Swift standard library provide?

Answer 9

is Type check
as Type cast

(No associativity, precedence level 132)

Question 10

What comparative binary operators does the Swift standard library provide?

Answer 10

< Less than
 Greater than
>= Greater than or equal
== Equal
!= Not equal
=== Identical
!== Not identical
~= Pattern match

(No associativity, precedence level 130)

Question 11

What conjunctive binary operator does the Swift standard library provide?

Answer 11

&& Logical AND

Left associative, precedence level 120

Question 12

What disjunctive binary operator does the Swift standard library provide?

Answer 12

|| Logical OR

Left associative, precedence level 110

Question 13

What assignment binary operators does the Swift standard library provide?

Answer 13

= Assign
*= Multiply and assign
/= Divide and assign
%= Remainder and assign
\+= Add and assign
-= Subtract and assign
<>= Right bit shift and assign
&amp;= Bitwise AND and assign
^= Bitwise XOR and assign
|= Bitwise OR and assign
&amp;&amp;= Logical AND and assign
||= Logical OR and assign

(Right associative, precedence level 90)

Question 14

What ternary operator does the Swift standard library provide?

Answer 14

?: Ternary conditional

Right associative, precedence level 100

Question 15

How are binary operator precedence rules applied?

Answer 15

At parse time, an expression made up of binary operators is represented as a flat list. This list is transformed into a tree by applying operator precedence

For example, the expression 2 + 3 * 5 is initially understood as a flat list of five items, 2, +, 3, *, and 5.

This process transforms it into the tree (2 + (3 * 5)).

Question 16

Which binary operator is this?

~=

Answer 16

Pattern match

Category: Comparative
No associativity
Precedence level 130

Question 17

Which binary operator is this?

||

Answer 17

Logical OR

Category: Disjunctive
Left associative
Precedence level 110

Question 18

Which binary operator is this?

*=

Answer 18

Multiply and assign

Category: Assignment
Right associative
Precedence level 90

Question 19

Which binary operator is this?

&-

Answer 19

Subtract with overflow

Category: Additive
Left associative
Precedence level 140

Question 20

Which binary operator is this?

> =

Answer 20

Greater than or equal

Category: Comparative
No associativity
Precedence level 130

Question 21

Which binary operator is this?

&=

Answer 21

Bitwise AND and assign

Category: Assignment
Right associative
Precedence level 90

Question 22

Which binary operator is this?

/=

Answer 22

Divide and assign

Category: Assignment
Right associative
Precedence level 90

Question 23

Which binary operator is this?

^=

Answer 23

Bitwise XOR and assign

Category: Assignment
Right associative
Precedence level 90

Question 24

Which binary operator is this?

-=

Answer 24

Subtract and assign

Category: Assignment
Right associative
Precedence level 90

Question 25

Which binary operator is this? ==

Answer 25

Equal Category: Comparative No associativity Precedence level 130

Question 26

Which binary operator is this? &*

Answer 26

Multiply, ignoring overflow Category: Multiplicative Left associative Precedence level 150

Question 27

Which binary operator is this? !==

Answer 27

Not identical Category: Comparative No associativity Precedence level 130

Question 28

Which binary operator is this? is

Answer 28

Type check Category: Cast No associativity Precedence level 132

Question 29

Which binary operator is this? >>

Answer 29

Bitwise right shift Category: Exponentiative No associativity Precedence level 160

Question 30

Which binary operator is this? ..

Answer 30

Half-closed range Category: Range No associativity Precedence level 135

Question 31

Which binary operator is this? %

Answer 31

Remainder Category: Multiplicative Left associative Precedence level 150

Question 32

Which binary operator is this? !=

Answer 32

Not Equal Category: Comparative No associativity Precedence level 130

Question 33

Which binary operator is this? *

Answer 33

Multiply Category: Multiplicative Left associative Precedence level 150

Question 34

Which binary operator is this? >>=

Answer 34

Right bit shift and assign Category: Assignment Right associative Precedence level 90

Question 35

Which binary operator is this? <<=

Answer 35

Left bit shift and assign Category: Assignment Right associative Precedence level 90

Question 36

Which binary operator is this? -

Answer 36

Subtract Category: Additive Left associative Precedence level 140

Question 37

Which binary operator is this? /

Answer 37

Divide Category: Multiplicative Left associative Precedence level 150

Question 38

Which binary operator is this?

Answer 38

Less than Category: Comparative No associativity Precedence level 130

Question 39

Which binary operator is this? +

Answer 39

Add Category: Additive Left associative Precedence level 140

Question 40

Which binary operator is this? ===

Answer 40

Identical Category: Comparative No associativity Precedence level 130

Question 41

Which binary operator is this? ^

Answer 41

Bitwise XOR Category: Additive Left associative Precedence level 140

Question 42

Which binary operator is this? <=

Answer 42

Less than or equal Category: Comparative No associativity Precedence level 130

Question 43

Which binary operator is this? &&=

Answer 43

Logical AND and assign Category: Assignment Right associative Precedence level 90

Question 44

Which binary operator is this? &+

Answer 44

Add with overflow Category: Additive Left associative Precedence level 140

Question 45

Which binary operator is this? %=

Answer 45

Remainder and assign Category: Assignment Right associative Precedence level 90

Question 46

Which binary operator is this? |=

Answer 46

Bitwise OR and assign Category: Assignment Right associative Precedence level 90

Question 47

Which binary operator is this? &/

Answer 47

Divide, ignoring overflow Category: Multiplicative Left associative Precedence level 150

Question 48

Which binary operator is this? &

Answer 48

Bitwise AND Category: Multiplicative Left associative Precedence level 150

Question 49

Which binary operator is this? ...

Answer 49

Closed range Category: Range No associativity Precedence level 135

Question 50

Which binary operator is this? <

Answer 50

Bitwise left shift Category: Exponentiative No associativity Precedence level 160

Question 51

Which binary operator is this? >

Answer 51

Greater than Category: Comparative No associativity Precedence level 130

Question 52

Which binary operator is this? |

Answer 52

Bitwise OR Category: Additive Left associative Precedence level 140

Question 53

Which binary operator is this? &%

Answer 53

Remainder, ignoring overflow Category: Multiplicative Left associative Precedence level 150

Question 54

Which binary operator is this? =

Answer 54

Assign Category: Assignment Right associative Precedence level 90

Question 55

Which binary operator is this? &&

Answer 55

Logical AND Category: Conjunctive Left associative Precedence level 120

Question 56

Which binary operator is this? as

Answer 56

Type cast Category: Cast No associativity Precedence level 132

Question 57

Which binary operator is this? ||=

Answer 57

Logical OR and assign Category: Assignment Right associative Precedence level 90

Question 58

Which binary operator is this? +=

Answer 58

Add and assign Category: Assignment Right associative Precedence level 90

Question 59

What are the rules for the assignment operator? =

Answer 59

The assigment operator sets a new value for a given expression. It has the following form: expression = value The value of the expression is set to the value obtained by evaluating the value. If the expression is a tuple, the value must be a tuple with the same number of elements. (Nested tuples are allowed.) Assignment is performed from each part of the value to the corresponding part of the expression. For example: ``` (a, _, (b, c)) = ("test", 9.45, (12, 3)) //a is "test", b is 12, c is 3, and 9.45 is ignored ``` The assignment operator does not return any value.

Question 60

What are the rules for the ternary operator? ? :

Answer 60

The ternary conditional operator evaluates to one of two given values based on the value of a condition. It has the following form: condition ? a : b If the condition evaluates to true, the conditional operator evaluates the first expression and returns its value. Otherwise, it evaluates the second expression and returns its value. The unused expression is not evaluated.

Question 61

What are the rules for the typecasting operator? as

Answer 61

If conversion to the specified type is guaranteed to succeed, the value of the expression is returned as an instance of the specified type. If conversion to the specified type is guaranteed to fail, a compile-time error is raised. Otherwise, if it’s not known at compile time whether the conversion will succeed, the type of the cast expresion is an optional of the specified type. At runtime, if the cast succeeds, the value of expression is wrapped in an optional and returned; otherwise, the value returned is nil.

Question 62

What are the rules for the type-testing operator? is

Answer 62

The is operator checks at runtime to see whether the expression is of the specified type. If so, it returns true; otherwise, it returns false. The check must not be known to be true or false at compile time.