Common Programming Concepts.

Question 1

By default Rust variables are ___ ?

Answer 1

immutable

Question 2

How do you make a variable mutable in Rust?

Answer 2

Adding “mut” in front of the variable name.

Question 3

What are some differences between variables and constants?

Answer 3

1. aren’t allowed to use “mut” with constants.
2. Constants are declared with the “const” keyword, not “let”.
3. The value of the constant type MUST be annotated.
4. Constants can be declared in any scope.
5. Constants may only be set to a constant expression.

Question 4

What is shadowing?

Answer 4

Declaring a new variable with the same name as a previous variable. The new variable shadows the previous variable. The first variable is shadowed by the second.

Question 5

If one variable shadows another, what value appears when the value is used?

Answer 5

The second one.

Question 6

How is shadowing different from marking a variable with mut?

Answer 6

A compile-time error will occur if we accidentally try to reassign to this variable without using the let keyword.

Question 7

What does using let in shadowing allow for?

Answer 7

Perform transformations on a value but have the variable be immutable after those transformations have been completed.

Question 8

What are two data type subsets found in Rust?

Answer 8

scalar and compound.

Question 9

Is Rust statically typed?

Answer 9

yes.

Question 10

What does a scalar data type represent?

Answer 10

A single value.

Question 11

What are the four primary scalar types found in Rust?

Answer 11

Integers, floating-point numbers, Booleans, and characters.

Question 12

What is an integer type?

Answer 12

A number without a fractional component.

Question 13

What does the i and u stand for with integer types?

Answer 13

Signed integer types start with i and unsigned start with u.

Question 14

List the various lengths for signed/unsigned integer types in Rust.

Answer 14

8-bit
16-bit
32-bit
64-bit
128-bit
arch

Question 15

What does signed and unsigned indicate for integer types?

Answer 15

Whether it’s possible for the number to be negative or positive. Signed can be negative and positive, unsigned is only for positive.

Question 16

How are signed integer stored?

Answer 16

Two’s compliment representation.

Question 17

What range of numbers can signed ints store?

Answer 17

-2^(n - 1) to 2^(n - 1) - 1 inclusive.

Question 18

What range of numbers can unsigned ints store?

Answer 18

0 to 2^(n - 1)

Question 19

What is Rust’s integer type default?

Answer 19

i32.

Question 20

What is a floating point type?

Answer 20

Numbers with decimal points.

Question 21

What are the two floating point types in Rust?

Answer 21

f32 and f64.

Question 22

What is the default floating point type in Rust

Answer 22

f64 - because on modern CPUs it’s roughly the same speed as f32 but is capable of more precision.

Question 23

How do you specify a boolean type?

Answer 23

bool.

Question 24

How many bytes is a boolean type?

Answer 24

one.

Question 25

How big is the char data type?

Answer 25

Four bytes in size and represents a Unicode Scalar Value.

Question 26

What is a compound type?

Answer 26

A type that can group multiple values into one type.

Question 27

What are two primitive compound types in Rust?

Answer 27

Tuples and arrays.

Question 28

What is a tuple?

Answer 28

A general way of grouping together some number of other values with a variety of types into one compound type.

Question 29

Do tuples have a fixed length?

Answer 29

Yes, once they are declared they cannot grow or shrink.

Question 30

How do you create a tuple?

Answer 30

Write a comma-separated list of values inside parentheses.

Question 31

How can we access tuple elements?

Answer 31

By destructuring (breaking down tuple into individual variables) or a . followed by an index.

Question 32

What is an array?

Answer 32

A compound data type that groups a collection of multiple values of the same type. Arrays have a fixed length.

Question 33

What are two reasons why arrays are useful?

Answer 33

When you want your data allocated on the stack rather than the heap or when you want to ensure you always have a fixed number of elements.

Question 34

What does [i32; 5] in “let a: [i32; 5] = [1, 2, 3, 4, 5];” do.

Answer 34

Specifies an array of 5 i32 integers.

Question 35

What does “let a = [3; 5];” do?

Answer 35

Initializes an array a of 5 elements all of the value 3.

Question 36

What is the keyword that allows you to to declare new functions?

Answer 36

fn

Question 37

In function signatures what must you declare?

Answer 37

The type of each parameter.

Question 38

What is a statement in Rust?

Answer 38

An instruction that performs some action and does not return a value.

Question 39

What is an expression in Rust?

Answer 39

An instruction that performs some action and does return some value.

Question 40

What does adding a ; to an expression do?

Answer 40

Turns it into a statement. It will not return anything.

Question 41

Where does a return type get declared in a function signature?

Answer 41

after the ->

Question 42

What must comments start with in Rust?

Answer 42

//

Question 43

Is if an expression or a statement in Rust?

Answer 43

An expression.

Question 44

Since if is an expression, what does it allow for?

Answer 44

Using it on the right side of a let statement.

Question 45

What are the three types of loops Rust has?

Answer 45

loop, while, for.

Question 46

What does the loop keyword do?

Answer 46

Tells Rust to execute a block of code over and over again forever or until you explicitly tell it to stop.

Question 47

What is a way to pass the result of a loop operation to the rest of your code?

Answer 47

Add the value you want returned after the break expression in the loop.

Question 48

What does a while loop do in Rust?

Answer 48

While a condition holds true, the code runs; otherwise, it exits the loop.

Question 49

What does a for loop do in Rust?

Answer 49

Executes some code for each item in a collection