Disruptive Programming Language Technologies

1. Disruptive Programming Language Technologies Todd A. Proebsting Microsoft Research April 24, 2002

2. April 24, 2002 Disruptive Programming Language Technologies 2 �Topic of Your Choice� �Where choice begins, Paradise ends� --- Arthur Miller Richard Hamming�s obituary (1998) The Innovator�s Dilemma by Clayton Christensen (1997) Perl, Visual Basic popularity:Their popularity is important (and good!)

3. April 24, 2002 Disruptive Programming Language Technologies 3 Richard Hamming�s Snare Richard Hamming�s three questions for new hires at Bell Labs: �What are you working on?� �What�s the most important open problem in your area?� �Why aren�t they the same?� (Ouch!) �You and Your Research� --- Richard Hamming (1986)

4. April 24, 2002 Disruptive Programming Language Technologies 4 The Least Important Open Problem in Programming Languages* Increasing program performance via compiler optimization Moore�s Law suffices Algorithms and design make the big difference Challenge: Name a single significant software product that relied on compiler optimization for viability. * The opinions expressed here are mine and mine alone. Microsoft disavows any connection to them�

5. April 24, 2002 Disruptive Programming Language Technologies 5 The Most Important Open Problem In Programming Languages* Increasing Programmer Productivity Write programs correctly Write programs quickly Write programs easily Why? Decreases support cost Decreases development cost Decreases time to market Increases satisfaction *Standard disclaimer.

6. April 24, 2002 Disruptive Programming Language Technologies 6 Programmer Productivity: 3 Approaches Process (software engineering) Controlling programmers Tools (static analysis, program generation) Important, but generally of narrow applicability Language design --- the center of the universe! Core abstractions, mechanisms, services, guarantees Affect how programmers approach a task (C vs. LISP) Assumptions, expectations, patterns(e.g., regular expressions, events, first-class functions, garbage collection, types�)

7. April 24, 2002 Disruptive Programming Language Technologies 7 Language Design: C vs. LISP What�s the difference between a C programmer and a LISP programmer? A LISP programmer knows the value of everything and the cost of nothing. A C programmer knows the cost of everything and the value of nothing.E.g., garbage collection, first-class functions, safety� The languages encourage this thinking: (map fn L) vs. while (*d++ = *s++); The �value investors� are reaping strong returns nowadays. (www.paulgraham.com)

8. April 24, 2002 Disruptive Programming Language Technologies 8 Programming Language Technologies:Recent Research vs. Progress(!) Recent (perpetual?) academic research: Type theory Functional programming Object-oriented programming Parallel programming Static analysis Compiler optimization Recent adoption: Perl, Python, Visual Basic, Java Almost void of innovation on type theory, functional programming, OO programming, optimization, etc! Perversely hopeful development for new language design efforts

9. April 24, 2002 Disruptive Programming Language Technologies 9 New Programming Language! Why Should I Care? The problem is not designing a new language It�s easy! Thousands of languages have been developed The problem is how to get wide adoption of the new language It�s hard! Challenges include Competition Usefulness Interoperability Fear Can other useful languages succeed? I think so. I�m avoiding the problem of how to design an �elite� language� �It�s a good idea, but it�s a new idea; therefore, I fear it and must reject it.� --- Homer Simpson

10. April 24, 2002 Disruptive Programming Language Technologies 10 The Innovator�s Dilemma (C. Christensen) �� why companies that did everything right---were in tune with their competition, listened to their customers, and invested aggressively in new technologies---still lost their market leadership when confronted with disruptive changes in technology�� --- the book�s back cover Why is C/C++ losing steam? ? Can we use the book�s lessons to help future language efforts? (Not the book�s intent�)

11. April 24, 2002 Disruptive Programming Language Technologies 11 The Innovator�s Dilemma:Cable-Actuated Excavators A �disruptive� technology hydraulic mechanisms Disadvantage in primary market small, unreliable Advantage in secondary market safe, attaches to tractor Sold in small, low-margin market independent contractors Established companies concentrate and innovate on primary market; ignore secondary capacity (for excavation) Timely improvements lessen disruptive technology�s liabilities, increasing markets, market share, margins, etc.

12. April 24, 2002 Disruptive Programming Language Technologies 12 The Innovator�s Dilemma: C A �disruptive� technology safe, GC�ed interpreters Disadvantage SLOW Advantage Rapid Application Develop Sold in small, low-margin market web developers, ISV�s (established competitor ignored market) Established companies concentrate on primary differentiator SPEED Timely improvements lessen disruptive technology�s liabilities, increasing markets, market share, margins, etc. Moore�s Law (for free!) RAD enhancements

13. April 24, 2002 Disruptive Programming Language Technologies 13 Perl, Visual Basic, Java vs. C(Programmer Productivity vs. Speed)

14. April 24, 2002 Disruptive Programming Language Technologies 14 Distinguishing/Disruptive Technologies:Alleviating Real Problems Perl Scripting with data structures (�duct tape�) Regular expressions Visual Basic Drag-and-drop environment (Windows for the masses) Component-friendly Java Browser applets Language integration yields pervasive patterns and abstractions

15. April 24, 2002 Disruptive Programming Language Technologies 15 Not A Dilemma---An Opportunity! Languages (or language technologies) that solve real problems can succeed Even if slow Even with simple types Even without academic significance Even without rocket science If useful Researchers need not despair Golden opportunity to use disruptive technology as a Trojan Horse for disseminating research ideas

16. April 24, 2002 Disruptive Programming Language Technologies 16 Future Disruptive Language Technologies(My Recurring Wish List) My criteria: technology must Have disadvantages Be ignored by recent PLDI andPOPL conferences (but not others) Alleviate real problems�What does it do?� For each candidate technology: 2 slides Opportunity what�s the issue? Current solutions what�s done now Proposal sketch of language solution Disadvantages why some (many?) will scoff Unmet needs benefits to adopters

17. April 24, 2002 Disruptive Programming Language Technologies 17 Candidate: Flight Data Recorders Opportunity: How do you debug a program that misbehaved after the error occured? Microsoft �Watson� experience 50% of crashes caused by 1% of bugs. Current solutions Ad hoc attempts to reproduce error condition Examine stack trace, program state (�core dump�)

18. April 24, 2002 Disruptive Programming Language Technologies 18 Disruptive Flight Data Recorders Add persistent, automatic �tracing� of function calls, events, I/O, etc. to the language run time.(E.g., AMOK/IDAL from IDA on CRAY-1) Important disadvantages Will slow every program down Will require storage Unmet needs Diagnostic data available to programmer --- 1/50 rule �Introspective� data available to program

19. April 24, 2002 Disruptive Programming Language Technologies 19 Candidate: Checkpoints/Undo Opportunity: Programs provide checkpoint or �undo� facilities in haphazard, unreliable ways.(E.g., MS Outlook, TurboTax, almost all tiny apps.) Current solutions: Checkpoint by saving document to a file Doesn�t scale well to unbounded undo Programmatic checkpoint by saving select data to file Subject to judgment (and error) Undo by saving operations and their inverse data Tedious Error-prone

20. April 24, 2002 Disruptive Programming Language Technologies 20 Disruptive Checkpoints/Undo Make checkpointing and undo (i.e., restoreto checkpoint) primitives in theprogramming language. Transactions. Important disadvantages External side-effects pose limitations(e.g., I/O) Slower than hand-crafted solution Unmet needs Simplicity Automation

21. April 24, 2002 Disruptive Programming Language Technologies 21 Candidate: Database (SQL?) Integration Opportunity: Facilitate access to values held in a database. Databases are too useful to hide behind SQL. Current solutions: Use SQL only Poor access to non-SQL resources Construct SQL queries by hand in host language No compile-time checks Tedious Embed SQL into host language via quoting Poor integration of host types and SQL types

22. April 24, 2002 Disruptive Programming Language Technologies 22 Disruptive Database Integration Proposal: Integrate DB types and host types Expose simple operations for Join, Project, Select, Sort Treat relations like structs Important disadvantages Type integration likely to include slow marshaling Lost opportunities to tune query processing Unmet needs One-language solution Lowered barrier to entry, more accessible functionality

23. April 24, 2002 Disruptive Programming Language Technologies 23 Candidate: Parsing Opportunity: Parsing is common and difficult in general. Current solutions: Parser generators for subsets of CFLs Regular expressions ala Perl Roll your own parser (and cross your fingers that nobody ever needs to maintain it)

24. April 24, 2002 Disruptive Programming Language Technologies 24 Disruptive Parsing �Scannerless Generalized LR Parsing� (or Earley parsing) could be integrated into a language Important disadvantages Slow Ambiguity presents its own problems Unmet needs Handle arbitrary CFL grammar Spec-driven systems adapt smoothly to change Confidence that parser meets spec XML grammar has 80+ productions�

25. April 24, 2002 Disruptive Programming Language Technologies 25 Candidate: Manipulating XML Opportunity: How to manipulate XML documents <students> <name>Grace</name> <name>Susan</name> <name>Annette</name> </students> Current solutions Marshal into and out of native data structures Use �Document Object Model� structures and API Use XML-specific sublanguage like XPath/XSLT �Java�s a drug you rub on venture capitalists to make them crazy.�--- John Doerr, (JavaOne 1996)

26. April 24, 2002 Disruptive Programming Language Technologies 26 Disruptive XML Manipulation Give XML first-class status for creation, pattern-matching and manipulation. E.g., x := <name>Grace</name>; <name>?y</name> := x; foreach <students>�?y�</students> := x do <S> Important disadvantages Declarative pattern matching may be slow Unmet needs XML integration into general purpose language Compile-time checking of XML manipulations.

27. April 24, 2002 Disruptive Programming Language Technologies 27 Candidate: Constraint Solvers Opportunity: Many applications have a subproblem that involves solving (or optimizing) a system subject to constraints Natural fit for visual layout problems (e.g., render tree structures, resize windows, summarize maps) Natural fit for optimization problems Current solutions Hand-rolled algorithms Library routines Third-party solvers Give up

28. April 24, 2002 Disruptive Programming Language Technologies 28 Disruptive Constraint Solvers Adding linear programming constraint solver (or, better, integer programming) to a programming language Important disadvantages Slower than tailored algorithmicsolutions Unmet needs Quick and dirty solutions Visual layout (Interviews-Tk?)

29. April 24, 2002 Disruptive Programming Language Technologies 29 Quandary: Distributed Programming Distributed programming is too hard Intuition says there must be an 80/20 disruptive technology out there. This would be huge with Web Services Suggestions welcome!

30. April 24, 2002 Disruptive Programming Language Technologies 30 A Final Prediction The next big programming language will be slower than what it replaces Why? The incumbent language will have been optimized relentlessly To replace it, the new language must offer something new that will be valuable even if slow.

31. April 24, 2002 Disruptive Programming Language Technologies 31 Shameless Self-Interest I manage the Programming Language Systems group in Microsoft Research We work on programming language design and implementation We appreciate small, simple solutions We�re a small group: Chris Fraser, Dave Hanson and me We�re recruiting! (Full-time and interns) Email: toddpro@microsoft.com

32. April 24, 2002 Disruptive Programming Language Technologies 32 The End