Your first Swift program

Write your code in a file named hello.swift:

print("Hello, world!")

• To compile and run a script in one step, use swift from the terminal (in a directory where this file is located):

To launch a terminal, press CTRL+ALT+T on Linux, or find it in Launchpad on macOS. To change directory, enter cddirectory_name (or cd .. to go back)

swift hello.swift

A compiler is a computer program (or a set of programs) that transforms source code written in a programming language (the source language) into another computer language (the target language), with the latter often having a binary form known as object code. (Wikipedia)

• To compile and run separately, use swiftc:

swiftc hello.swift

This will compile your code into hello file. To run it, enter ./, followed by a filename.

./hello

• Or use the swift REPL (Read-Eval-Print-Loop), by typing swift from the command line, then entering your code in the interpreter:

Code:

func greet(name: String, surname: String) {
    print("Greetings \(name) \(surname)")
}

let myName = "Homer"
let mySurname = "Simpson"

greet(name: myName, surname: mySurname)

Let’s break this large code into pieces:

• func greet(name: String, surname: String) { // function body } - create a function that takes a name and a surname.
• print("Greetings \(name) \(surname)") - This prints out to the console “Greetings “, then name, then surname. Basically \(variable_name\) prints out that variable’s value.
• let myName = "Homer" and let mySurname = "Simpson" - create constants (variables which value you can’t change) using let with names: myName, mySurname and values: "Homer", "Simpson" respectively.
• greet(name: myName, surname: mySurname) - calls a function that we created earlier supplying the values of constants myName, mySurname.

Running it using REPL:

swiftfunc greet(name: String, surname: String) {print("Greetings \(name) \(surname)")}let myName = "Homer"let mySurname = "Simpson"greet(name: myName, surname: mySurname)

Press CTRL+D to quit from REPL.