Infix functions in DSLs in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an infix function in Kotlin?

An infix function is a special kind of function that can be called using infix notation, meaning you can write it between its receiver and argument without dots or parentheses, making code more readable and natural.

beginner

How do you declare an infix function in Kotlin?

You declare an infix function by adding the keyword infix before the function name. It must be a member function or an extension function with a single parameter and no varargs or default values.

intermediate

Why are infix functions useful in DSLs (Domain Specific Languages)?

Infix functions make DSL code look cleaner and more like natural language, improving readability and expressiveness by allowing calls without dots or parentheses, which fits well with DSL style.

beginner

Example: What does this Kotlin code do?<br>

infix fun Int.times(str: String) = str.repeat(this)

This defines an infix function times that repeats a string a given number of times. For example, 2 times "Hi" returns "HiHi".

intermediate

What are the restrictions on parameters for infix functions?

Infix functions must have exactly one parameter. They cannot have varargs, default parameter values, or multiple parameters.

Which keyword is used to declare an infix function in Kotlin?

A fun

B inline

C infix

D override

The infix keyword marks a function as infix, allowing it to be called without dots or parentheses.

What is a requirement for the parameter of an infix function?

A It must be a vararg parameter

B It can have multiple parameters

C It must have default values

D It must be a single parameter without default values

Infix functions must have exactly one parameter and cannot have default values or varargs.

How would you call an infix function named connect on an object a with argument b?

A a.connect(b)

B a connect b

C connect(a, b)

D connect a b

Infix functions are called using infix notation: a connect b without dots or parentheses.

Why are infix functions popular in Kotlin DSLs?

A They make code look more natural and readable

B They improve performance

C They allow multiple parameters

D They require less memory

Infix functions improve readability and make DSL code look like natural language.

Which of these is NOT allowed in an infix function declaration?

A Multiple parameters

B Single parameter

C Extension function

D Member function

Infix functions cannot have multiple parameters; they must have exactly one.

Explain what an infix function is and how it helps in creating DSLs in Kotlin.

Think about how you write code that reads like a sentence.

Describe the rules and restrictions for declaring an infix function in Kotlin.

Focus on the function signature and keywords.