Transcript Dylan: Charles Grove, Philip Oliver

Dylan
An Object Oriented Dynamic
Language
Dylan Overview
Short for “Dynamic Langage”
 General-purpose
 Object-oriented
 Attempts to combine functionality of:

 Lisp
 Smalltalk
 C++
Why Dylan?
Apple's Advanced Technology Group
 Different people using Lisp, SmallTalk, and
C++
 Wanted a language to appease all three
groups

History and Downfall



Considered for use with the Apple Newton (the protoPDA)
Kept as general purpose Mac programming language
Much work on compilers and IDEs while Dylan still in
development.





For Mac by Apple
For Windows by Harlequin
“d2c” compiler for UNIX by CMU
Development scrapped in mid-1990s due to budget cuts.
Java became popular instead.
Dylan: Language Concepts
All objects are classes and functions.
 All objects are “typed”.
 Garbage Collection

Class Definition
define class <rock> (<object>)
slot initial-position :: <float>,
required-init-keyword: position:;
slot initial-velocity :: <float>,
required-init-keyword: velocity:;
end class;
Find Position Function
define function find-position-and-velocity (rock ::
<rock>, time :: <float>)
 (position :: <float>, velocity :: <float>) values(-4.9
* time * time
+ rock.initial-velocity * time
+ rock.initial-position,
-9.8 * time + rock.initial-velocity);
end function;
Print Function
define function print-position-and-velocity (rock ::
<rock>, time :: <float>)
 ()
let (p, v) = find-position-and-velocity(rock, time);
format-out("Position: %=m, Velocity: %=m/s\n",
p, v);
end function;
Use of Class and Functions
define variable *rock* =
make(<rock>, position: 10.0, velocity: 0.0);
print-position-and-velocity(*rock*, 1.0);
*rock*.position := “5.0”;
position(*rock*) := “5.0";
position-setter(“5.0", *rock*);
Dylan vs C++
Dylan as a number of features that distinguish it
from C++ including:
 automatic memory management
 clean, consistent syntax
 fully and consistently object-oriented model
 dynamic as well as static type checking
 support for incremental compilation
 first-class functions and classes
Dylan vs Java
Dylan already has solutions to the Javas problems:
 multiple implementation inheritance
 multiple argument method dispatch
 pure object types
 no casting required
 extensible syntax
 good iteration/collection integration