Dylan differs from most mainstream languages in several subtle ways. If you're really immersed in how one particular language works, you'll have to let go of some of your knowledge. Dylan's generic functions and access control, for example, are probably unfamiliar. You'll have to learn these all over again, but will be rewarded with more flexibility when you do.
We recommend using the Open Dylan "Interactor" when you first start learning Dylan since it provides instant feedback. (The Interactor is analogous to a Lisp Listener or a Python REPL.) Open Dylan also allows downloading code into running applications, which can be extremely useful when learning the language and making many rapid modifications.
The following references might be good places to start:
Twelve standalone code fragments show off the features of the Dylan programming language (well, eight of them currently). If you want to get a feel for things, this might be a good place to start.
A quick and dirty introduction to Dylan for reasonably skilled programmers. It covers the diffences between Dylan and other popular programming languages.
A good Dylan tutorial by several Harlequin employees.
Steve Strassmann wrote a brief article on Dylan for develop. It covers classes, functions and modules, and provides good examples.
The official Dylan reference, available online or as a well-bound softcover book. If you're the type who likes to go right to the language reference to learn, then by all means go here first, but most people seem to agree this isn't the easiest way to learn Dylan. If you already know a smattering of Dylan, and can only get one book, this is your best bet.
A set of notes on the pitfalls of translating a Common Lisp program into Dylan. Should be of interest to people wishing to migrate Allegroserv or other CL applications.
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