Dylan An Object Oriented Dynamic Language Dylan Overview

Dylan An Object Oriented Dynamic Language

Dylan Overview Short for “Dynamic Langage” n General-purpose n Object-oriented n Attempts to combine functionality of: n ¨ Lisp ¨ Smalltalk ¨ C++

Why Dylan? Apple's Advanced Technology Group n Different people using Lisp, Small. Talk, and C++ n Wanted a language to appease all three groups n

History and Downfall n n n Considered for use with the Apple Newton (the proto. PDA) 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 ¨ “d 2 c” compiler for UNIX by CMU ¨ n n Development scrapped in mid-1990 s due to budget cuts. Java became popular instead.

Dylan: Language Concepts All objects are classes and functions. n All objects are “typed”. n Garbage Collection n

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>) Þ (position : : <float>, velocity : : <float>) values(-4. 9 * 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>) Þ () let (p, v) = find-position-and-velocity(rock, time); format-out("Position: %=m, Velocity: %=m/sn", 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: n automatic memory management n clean, consistent syntax n fully and consistently object-oriented model n dynamic as well as static type checking n support for incremental compilation n first-class functions and classes

Dylan vs Java Dylan already has solutions to the Javas problems: n multiple implementation inheritance n multiple argument method dispatch n pure object types n no casting required n extensible syntax n good iteration/collection integration