Lars Bak & Gilad Bracha
Monday, October 10, 2011

DART: A STRUCTURED WEB
PROGRAMMING LANGUAGE• New programming language• New programming tools• New open source project
WARNING: THIS IS ONLY A TECHNOLOGY PREVIEW

Monday, October 10, 2011

SPEAKER INTRODUCTION
Lars Bak

Gilad Bracha
BetaSelf
OOVM

25 years

Monday, October 10, 2011

V8Text
Dart

Strongtalk

JVMs

JLS
Newspeak

25 yearsDART AGENDA• The motivation• The language• Code samples• Demos• The open source project

Monday, October 10, 2011

CURRENT WEB: THE GOOD PARTS• Developing small applications is easy
• Platform independence• No installation of applications• Supports incremental development• ... and it is everywhere

Monday, October 10, 2011

CURRENT WEB: THE BAD PARTS• Developing large scale applications is hard
• Hard to ﬁnd the program structure• Lack of static types• No support for libraries• Tools support is weak
• Startup performance is bad

Monday, October 10, 2011

INNOVATION IS ESSENTIAL• We believe Dart ﬁlls a vacuum• The competition is NOT JavaScript• ... but fragmented mobile platforms

Monday, October 10, 2011HISTORY BEHIND DART
I’m Kasper• After several years working on V8 for Chrome• Last year, Kasper Lund & I experimented with Spot
• a new simple language for the web• based on the experiences from JavaScript• Spot was the prelude for the Dart project

Monday, October 10, 2011

SO WHAT IS DART?

• A simple and unsurprising OO programming language• Class-based single inheritance with interfaces• Optional static types• Real lexical scoping• Single-threaded• Familiar syntax

Monday, October 10, 2011

A DIFFERENT TYPE-CHECKER• A conventional type-checker is a lobotomized theorem prover• Tries to prove program obeys type system• If it can't construct a proof - program is considered invalid“Guilty until proven innocent”• In Dart, you are innocent until proven guilty

Monday, October 10, 2011

DART TYPES AT RUNTIME• During development one can choose to validate typesassert(o === null || o is T);• T x = o;• By default, type annotations have no eﬀect and no cost
• Code runs free

Monday, October 10, 2011

OPTIONAL TYPES• Static checker provides warnings; tuned to be unobtrusive• Type annotations have no eﬀect except ...
• During development, you can check dynamic types againstdeclarations

Monday, October 10, 2011

ISOLATES• Inspired by Erlang, Dart has isolates• Lightweight units of execution• Each isolate is conceptually a process• Nothing is shared• All communication takes place via message passing• Isolates support concurrent execution

Monday, October 10, 2011

DART IS NOT DONE
• Reﬂection support?
• Rest arguments and enums?
• Pattern matching for easy message decoding like in Erlang?
• What about Chrome?
• ... please give feedback by joining the discussions

Monday, October 10, 2011

DART EXECUTION
Dart Source

DartC
JavaScript
EngineMonday, October 10, 2011

Tools

Text

Snapshot

Dart VMDART PERFORMANCE
Relative performance compared to JavaScript on V8
Benchmark
VM
DartC
Mandelbrot:
18.2%
88.7%
DeltaBlue:
56.6%
52.2%
Richards:
46.0%
70.9%
NBody:
35.8%
63.6%
BinaryTrees:
77.3% 104.3%
Fannkuch:
53.8%
22.3%
Meteor:50.3%
42.1%
Details:- V8 revision 3.5.5.
- DartC used with the -optimize flag

Monday, October 10, 2011

SNAPSHOTTING IN THE DART VM• Process of serializing the heap after loading the application• Loading 54173 lines of Dart code takes 640 ms• Loading same application from a snapshot takes 60 ms• Startup > 10x fasterMonday, October 10, 2011

WEB APPLICATION IN DART• Newsreader completely written in Dart
• App code: 3210 LOC• UI library code: 13200 LOC• Animation yields 30 fps• Code is part of the open source project

Monday, October 10, 2011

DART EDITOR• Editor for constructing and browsing Dart applications• Lightweight editor based on Eclipse components• Code is part of the open source project

Monday, October 10, 2011

DART OPEN SOURCE PROJECT• The Dart web site: http://dartlang.org• Dart language speciﬁcation• Dart language tutorial• The Dart project: http://dart.googlecode.com• Libraries and code samples• Dart virtual machine• Dart to JavaScript compiler

Monday, October 10, 2011

DART IS A TECHNOLOGY PREVIEW• Dart: a programming language for the web• Two execution modes, Dart VM or JS Engine• Compatible with the current web• Please try it out and participate

Monday, October 10, 2011

Q&A
Monday, October 10, 2011