Declaration

Functions in THP have a different syntax than PHP.

Function names must begin with a lowercase letter.

Minimal function

The following code shows a function without parameters and without return type:

fun say_hello() {
╰╴No statement matched
  print("Hello")
}

say_hello()
thp

Functions are called the same way as in PHP.

With return type

If your function return any value, annotating the return type is mandatory, and it’s done by placing an arrow -> followed by the return datatype:

fun get_random_number() -> Int {
╰╴No statement matched
  return Random::get(0, 35_222)
}

val number = get_random_number()
thp

It’s an error to return from a function that doesn’t declare a return type:

fun get_random_number() {
╰╴No statement matched
  // Error: the function does not define a return type
  return Random::get(0, 35_222)
}
thp

You can omit the return keyword if it’s placed on the last expression on the function:

fun get_random_number() -> Int {
╰╴No statement matched
  // The last expression of a function is
  // automatically returned
  Random::get(0, 35_222)
}
thp

Function parameters

Parameters are declared like C-style languages: Type name, separated by commas.

fun add(Int a, Int b) -> Int {
╰╴No statement matched
  return a + b
}

val result = add(322, 644)
thp

THP has different semantics on parameters concerning pass by value, pass by reference and copy on write. This is detailed in another chapter.

Generic types

Functions can declare generic types by using the syntax [Type].

The following example declares a generic T and uses it in the parameters and return type:

fun get_first_item[T](Array[T] array) -> T {
╰╴No statement matched
  array[0]
}

val first = get_first_item[Int](numbers)
// The type annotation is optional if the compiler can infer the type

val first = get_first_item(numbers)
thp

Default arguments

TBD

Variadic arguments

TBD

Signature

() -> ()
╰╴No statement matched
() -> (Int)
(Int, Int) -> (Int)
[T](Array[T]) -> (T)
thp

Named arguments

fun html_special_chars(
╰╴No statement matched
  String input,
  Int? flags,
  String? encoding,
  Bool? double_encoding,
) -> String {
  // ...
}

html_special_chars(input, double_encoding: false)
thp

TBD: If & how named arguments affect the order of the parameters

Named arguments with different names

fun greet(
╰╴No statement matched
  String name,
  String from: city,
) {
  print("Hello {name} from {city}!")
}

greet("John", from: "LA")
thp