Hello, World!

The canonical “Hello World” program in Dylan.

File library.dylan:

Module: dylan-user

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

define module hello
  use format-out;
end;

File hello.dylan:

Module: hello

format-out("Hello!\n");

How it works:

1. Every Dylan program defines a library and at least one module in that library, and the simple Hello World program is no exception.
2. Every source file must have a “Module” header to say which module its definitions should be in. The library is defined in the pre-existing “dylan-user” module.
3. The top level expressions in each source file are executed in order when the library is loaded, so there is no need for a “main” method here.