thp/doc-generator/markdown/en/docs/latest/functions/parameters.md

Function parameters

Function with 1 parameter

Place the parameter's datatype after the function's name, then the name of the parameter.

For example, a function that takes a Str as parameter is defined as follows:

fun sayHello(Str name) =
    // Body of the function

Then the parameter name can be used.

fun sayHello(Str name) =
    print("Hello {name}")

Function with 2 or more parameters

The parameters are separated with commas:

// 2 parameters: x and y, both Int
fun add(Int x, Int y) -> Int =
    x + y

// 3 parameters
fun substring(Str input, Int start, Int end) -> Str =
    // Logic...

And so on.

Generic parameters

Generic parameters consist of an uppercase letter enclosed in square brackets. They are placed after the function name, but before the parameters list.

fun getItemAt[T](Array[T] arr, Int pos) -> T =
    // Function body

When calling the function, the generic parameter is placed in the same position.

val thirdName = getItemAt[String](names, 2)

If the generic parameter can be inferred, it's not necessary to put it.

// Will be a String, inferred
val thirdName = getItemAt(names, 2)

Named parameters

When calling a function you can link the name of an argument to its value. In the following function, substring has 3 parameters: string, start and end.

fun substring(Str string, Int start, Int end) =
    // Body of the function

Then, when calling the function, you can specify each parameter and their values.

// Without named parameters
substring("Hello, world!", 7, 12)

// With named parameters
substring(string: "Hello, world!", start: 7, end: 12)

substring(
    string: "Hello, world!",
    start: 7,
    end: 12,
)

This will return "world".

You can do computations with named parameters as well.

substring(string: "Hello, world!", start: 12 - 5, end: 48 / 4)

substring(
    string: "Hello, world!",
    start: 12 - 5,
    end: 48 / 4,
)