Skip to content

Latest commit

 

History

History
63 lines (52 loc) · 2.58 KB

invoking-function.md

File metadata and controls

63 lines (52 loc) · 2.58 KB
Raw

Theory: Invoking functions

As you remember, we have discussed functions before. What is a function, though? How can we tame them? A function is a sequence of instructions, we can invoke it from a program by calling its name. Functions represent subprograms, and they perform some actions, for example, printing data to the standard output, calculating a square root, and so on.

  • 함수의 정의에 대해 간단히 소개하면 Arguments 를 받아서 결과를 낼 수 있는 것으로 (안내도됨.) 그냥 이름을 가진 작은 프로그램이라고 생각하면 됨.

Functions arguments

When we want to use a function, we can invoke (or call) it using its name followed by parentheses. If a function takes one or more arguments (input data), they should be passed in the parentheses.

In the example below, we invoke the println function with a single-string argument:

val text = "Hello"
println(text)

This function can also take no arguments at all to print a new line:

function1() // invokes function1 without an argument
function2(arg1) // invokes function2 while passing an argument
function3(arg1, arg2) // invokes function3 while passing two arguments
// ... and so on
  • 함수의 호출에 있어서 Argument 는 필요할 수도 있고 필요없을 수도 있다.

Producing a result

Some functions not only take arguments but also produce (return) some results. You can also assign it to a variable:

val result = function(arg)

Functions that take arguments and produce a result look like regular math functions.

For example, let's take a look at a math function that returns the absolute value of a number:

val number = -10
val nonNegNumber = Math.abs(number) // it takes -10 and returns 10

A benefit of using functions is that you don't need to implement anything, just invoke a function and it will work.

All functions return a result, even the println function.

val result = println("text")
println(result) // kotlin.Unit

The result is a special value called Unit that practically means no result.

  • 함수의 결과를 변수로 받아오는게 가능하다.
  • 하나의 클래스에서 여러개의 함수를 그룹처럼 가지고 있는게 가능하다. (static function 으로 가지고 있는걸 말하는듯)
  • 코틀린에서는 함수가 반환을 하지 않더라도 변수로 함수를 호출한 결과를 받아오면 값이 들어간다고 한다. kotlin.Unit 이라는 값이 전달되고 의믜는 No Result 이다.