10. Representing unknown values

Question 1

Julia as a Second Language

What does a null or nil object (used in other programming languages but not in Julia) represent?

Answer 1

Question 2

Julia as a Second Language

What is a big problem with using null or nil in a programming language?

Answer 2

Question 3

Julia as a Second Language

What object in Julia is the closest thing Julia has to a null or nil object?

Answer 3

Question 4

Julia as a Second Language

What is a nothing object and what type is it?

Answer 4

Question 5

Julia as a Second Language

How many instances of the nothing object can a program have?

Answer 5

Question 6

Julia as a Second Language

How can you create an object that is empty, similar to the nothing object?

Answer 6

Question 7

Julia as a Second Language

What happens when you call composite type with no fields?

Answer 7

Question 8

Julia as a Second Language

What is P{T} ?

Answer 8

Question 9

Julia as a Second Language

What is Union ?

Answer 9

Question 10

Julia as a Second Language

How will the different types included in a Union{} be related to each other?

Answer 10

Question 11

Julia as a Second Language

Does the order of Union type parameters matter?

Answer 11

Question 12

Julia as a Second Language

How do you represent missing values in Julia?

Answer 12

Question 13

Julia as a Second Language

What happens to a mathematical operation if it contains a missing object?

Answer 13

Question 14

Julia as a Second Language

Any data with a missing object in it mathematically evaluates to missing. How can can the mathematical evaluation be told to skip the missing data?

Answer 14

Question 15

Julia as a Second Language

What is NaN ?

Answer 15

Question 16

Julia as a Second Language

What are the differences and similarities of these objects: nothing, missing, NAN, Undefined ?

Answer 16