About

What is Dylan?

Dylan is a programming language that was originally created at Apple Computer in the early 1990s. It was subsequently developed by teams at Apple Computer, Harlequin, and Carnegie Mellon University. The Harlequin implementation of Dylan lives on today as an open source project, Open Dylan.

Dylan was strongly influenced by the Scheme and Common Lisp programming languages, but uses a syntax derived from the Algol and Pascal tradition.

The Introduction to Dylan gives a nice and easy overview of the language.

Why Dylan?

We love the language and find it both productive and satisfying to work with. A craftsman should love his tools and Dylan is what makes us happy.

But why?

Some things that we like about Dylan are:

• The syntax is clear and consistent. While it is sometimes verbose, it remains highly readable.
• The type system allows for static typing as well as a looser, more dynamic view of the world.
• It provides multi-methods and a consistent and ever-present object system.
• It provides for a mixture of object-oriented and functional programming.
• It allows for multiple return values, rest arguments, and keyword arguments.
• It has a condition system like Common Lisp.
• It has a powerful macro system.
• Dylan compiles to an efficient executable.

Overall, Dylan gives the programmer a flexible set of primitives to build on and these primitives mesh together well. You don't find yourself wondering how various language features fit together.

We've used many other languages in the past and in the intervening years since discovering Dylan, but keep getting drawn back. Dylan is something special.

What does Dylan look like?

Much like pictures are worth a thousand words, snippets of a programming language can help to communicate the essence of the language.

A simple factorial, using recursion and multi-method dispatch:

define method factorial (n == 0) 1 end;
define method factorial (n == 1) 1 end;

define method factorial (n)
  n * factorial(n - 1)
end;

A simple fibonacci sequence generator, using a closure:

define function make-fibonacci()
  let n = 0;
  let m = 1;
  method ()
    let result = n + m;
    n := m;
    m := result  // return value
  end
end;

define constant fib = make-fibonacci();

for (i from 1 to 15)
  format-out("%d ", fib())
end;

Learning More About Dylan

Dylan has a large amount of documentation available:

• Introduction to Dylan:

  A tutorial is written primarily for those with solid programming experience in C++ or another object-oriented, static language. It provides a gentler introduction to Dylan than does the Dylan Reference Manual (DRM).

• Dylan Reference Manual:

  The official definition of the Dylan language and standard library.

• Dylan Programming Guide:

  A good, book length Dylan tutorial by several Harlequin employees.

• OpenDylan Documentation:

  All of the OpenDylan documentation.