The Hello World program with a Quit button

This program just opens a small window displaying the message "Hello, world!" and a Quit button. The window will look something like this (depending on your setup):

Here is the source code:

import AllFudgets

main = fudlogue (shellF "Hello" (labelF "Hello, world!" >+< quitButtonF))

Things to note

• This program is a small extension of the previous one. We have replaced

  (labelF "Hello, world!")

  with

  (labelF "Hello, world!" >+< quitButtonF)

  The operator >+< is parallel composition of fudgets (see the circuit diagram in the manual page).

• The fudget quitButtonF is a button which quits the program when pressed.

• The automatic layout system chose to use a vertical composition of the two parts in this user interface.

• The window manager usually provides a quit button in the window frame or something equivalent, so there is usually no need to put an extra quit button in the program.