Hello, World!

The canonical “Hello World” program in Dylan.

File library.dylan:

Module: dylan-user

define library hello
  use dylan;
  use io, import: { format-out };

define module hello
  use dylan;
  use format-out;

File hello.dylan:

Module: hello



The deft new application command (called dylan new application in Open Dylan 2024.1 and older releases) will create these files for you, along with a test suite and build files.

How it works

  • Every Dylan program defines a library and at least one module in that library, and the simple Hello World program is no exception.

  • Every source file has a Module: header to say which module its definitions should be in. The library and module themselves are defined in the pre-existing dylan-user module.

  • The top level expressions in each source file are executed in order when the library is loaded, so there’s no need for a main function.