.. _general-hello-world-compile-run:

Hello World - Compile and Run
=============================

.. code-block:: idris

  module Main

    data Tree a = Leaf
                | Node (Tree a) a (Tree a)

    inorder : Tree a -> List a
    inorder Leaf = []
    inorder (Node left a right) = inorder left ++ [a] ++ inorder right

    tree : Tree String
    tree = Node
            (Node
              (Node Leaf "3" Leaf)
              "+"
              (Node Leaf "7" Leaf))
            "/"
            (Node Leaf "2" Leaf)

    main : IO ()
    main = printLn $ inorder tree

**Compile**

``idris2 helloworld.idr -o main``

**Run**

.. code-block:: shell

  % build/exec/main
  ["3", "+", "7", "/", "2"]