THE COBRA
PROGRAMMING LANGUAGE
At the SoCal Piggies, Feb 2008
cobra-language.com
Chuck Esterbrook
INTRO
Cobra is a new language (sub 1.0)
Object-oriented, imperative
Embraces unit tests, contracts and more
General purpose
Runs on .NET & Mono
Windows, Mac, Linux, Solaris, etc.
MOTIVATION
Productivity boosters are scattered across languages
Clean syntax (Python, Ruby)
Run-time performance (C#, C++)
Static and dynamic typing (Objective-C, VB)
Contracts (Eiffel, Spec#)
Nil tracking (Spec#, iihtdioa.C#)
Not mutually exclusive!
I WANT IT ALL
No more jumping around
Clean syntax (Cobra, Python, Ruby)
Run-time performance (Cobra, C#, C++)
Static and dynamic typing (Cobra, Objective-C, VB)
Contracts (Cobra, Eiffel, Spec#)
Nil tracking (Cobra, Spec#, iihtdioa.C#)
Goal is maximum productivity
INFLUENCES
The “Big Four”
Python, C#, Eiffel, Objective-C
Others
Visual Basic, D, Boo, Smalltalk
Originally conceived of as a cross between
Python and Objective-C
NO NIL UNLESS I SAY SO
NullReferenceExceptions happen
one at a time at
run-time
Method sigs don’t indicate if they return or accept it
def nodeFor(name as String) as Node?
def nodeFor(name as String?) as Node?
Compile-time detection happens
many times at
compile-time
SQUEAKY CLEAN SYNTAX
Python-like
Light on symbols, indented blocks, keywords
list literals, dict literals, (soon) set literals
in / not in, is vs. ==
But even cleaner!
Straight forward properties
Other tweaks
DYNAMIC OR STATIC? BOTH!
Programmers should choose,
not language designers
Objective-C has been doing it for ~20 years
Others include Visual Basic and Boo
def add(a as int, b as int) as int
def add(a, b) as dynamic
There are pros and cons to both
Don’t have to switch languages to switch approaches
DYNAMIC IS CLEARLY BEST!
def add(a, b) as dynamic
return a + b
Flexible
Fast coding and prototyping
Less brittle w.r.t. changes
More reusable
STATIC IS CLEARLY BEST!
def nodeFor(name as String) as INode?
Compile-time detection of errors
Multiple errors reported at once
Fast at run-time
Slim too (no boxing)
Easy Intellisense
PERFORMANCE
Performance can be very important
... financial analysis, video games, compilers, AI, ...
Performance can
become important
Yahoo Mail: Python, then C++
AI company: Ruby prototype, then C++
Cobra compiles and leans towards static
“i = 5” infers “i” as an “int”
SCRIPTING CONVENIENCE
Compile and run in one command:
> cobra foo.cobra
#! line on Unix-like systems
Clean syntax is a hallmark of
some scripting languages
Dynamic binding is a hallmark of scripting languages
CONTRACTS
def nodeFor(name as String) as INode?
require name.length
ensure
result.name.toLower == name.toLower
...
Supports invariant, old, result and implies
Inheritance works
Eiffel-style: the “real thing”
Future? Integrate with Spec# backend
UNIT TESTS
def capped(s as String) as String is shared
test
assert Utils.capped(‘aoeu’) == ‘Aoeu’
assert Utils.capped(‘’) == ‘’
expect NullArgumentException
Utils.capped(nil) # ahem
body
...
Same motivations as doc strings:
localized, encourage use, get people on same page
ACCURATE MATH IN 2008
0.1 added ten times is what?
In most languages: not 1.0!
Python:
>>> .1+.1+.1+.1+.1+.1+.1+.1+.1+.1
0.99999999999999989
>>> assert 1.0 == .1+.1+.1+.1+.1+.1+.1+.1+.1+.1
AssertionError
Cobra supports both decimal and float (64-bit)
Defaults to decimal because it’s 2008
THE COMPILER
Self-implemented a.k.a “self-hosted”
Usual phases:
tokenize, parse, AST nodes, analysis, code gen
Something different: chose C# as backend over IL
Growing number of “super-VM” features in C#
Faster implementation
Piggy back on error checking and cmd line options
VEND TO C# AND VB
You can vend class libraries to C# and VB,
both technically and practically.
Super-C# features like non-nil degrade gracefully
Technically: .NET/Mono DLLs and CLI-style classes
Practically
Cobra favors .NETisms like generic lists
Can embed Cobra run-time (avoid Cobra.Lang.dll)
WEAKNESSES
Maturity - still gaps and some bugs
More nifty features not implemented
than I would prefer (upcoming slide)
No IDE plug-ins
No interactive prompt
COMPARED TO PYTHON
Best place: http://cobra-language.com/docs/python/
Better error checking, Compile-time nil tracking
First class contracts and unit tests
Speed, Default to accurate math
Syntax, Self-hosted
Disadvantges: Maturity, Docs, Less malleable
FEBRUARY 2008!
From January presentation:
An exciting month for Cobra!
Leaving “stealth mode”
(Lang.NET, InfoWorld)
Open sourcing the compiler (tonight)
Discussion forums
(done)
Wiki
(next week?)
Issue tracker
(next week?)
THIS WEEK == CRAZY WEEK
Present Cobra to Pythons
eWeek article on Friday
Open the source on Thu/Friday
Cut a new release on Thu/Friday
Hold down a job.
Saturday: Hopefully get Trac working.
MARCH 2008!
More fixes and refinements
Apply patches
Start Visual Cobra
More fixes and refinements
Release early, Release often!
COMMERCIALISM
In 2007, I worked full time on Cobra.
Paid rent with savings (and a poker tournament).
In 2008, return to contracting.
Less time for Cobra. :-(
Ideas:
Visual Cobra / VS PlugIn
Book, Web site ads
Microsoft | Novell sponsors Cobra :-)
FUTURE FEATURES
Context: Be the best, most productive, high-level,
general-purpose OO language.
Full LINQ and friends (lambdas, etc.)
Language level reg-ex
Built-in Set
mix-ins / traits / ...
DLR integration
MORE FUTURE FEATURES
More sophisticated unit test features
Units of measurement (feet, meters, ...)
Compile-time analysis of contracts
def foo(thing)
require
thing responds to (get name as String)
Multiple backends
JVM, Objective-C, D, LLVM, Parrot, ...
THE FAR FUTURE
Parallel programming
Futures / lazy arguments
Macros
Would be nice to leverage .NET advances as with
generics, LINQ, etc.
THE FAR, FAR FUTURE
Cobra has compile-time nil tracking and contracts
Microsoft has Pex and Spec# / Boogie
Could we eventually get here:
Detect all technical errors at compile-time
in < 60 secs
Leave slower run-time tests and round-tripping
to domain logic issues only
JOIN THE FUN
You can help!
Participate in the forums, wiki and issue tickets
Write sample code
Blog, discuss, write
Write a cool app or library
Patch the open source compiler
WEB SITE
cobra-language.com
cobra-language.com/docs/why
cobra-language.com/docs/python
Sample programs, How To, Documentation, Forums
cobralang.blogspot.com
Chuck.Esterbrook@gmail.com
