Posts in this category
- Current State of Exceptions in Rakudo and Perl 6
- Meet DBIish, a Perl 6 Database Interface
- doc.perl6.org and p6doc
- Exceptions Grant Report for May 2012
- Exceptions Grant Report -- Final update
- Perl 6 Hackathon in Oslo: Be Prepared!
- Localization for Exception Messages
- News in the Rakudo 2012.05 release
- News in the Rakudo 2012.06 release
- Perl 6 Hackathon in Oslo: Report From The First Day
- Perl 6 Hackathon in Oslo: Report From The Second Day
- Quo Vadis Perl?
- Rakudo Hack: Dynamic Export Lists
- SQLite support for DBIish
- Stop The Rewrites!
- Upcoming Perl 6 Hackathon in Oslo, Norway
- Pattern Matching and Unpacking
- Rakudo's Abstract Syntax Tree
- The REPL trick
- A shiny perl6.org site
- Creating an entry point for newcomers
- An offer for software developers: free IRC logging
- Announcing try.rakudo.org, an interactive Perl 6 shell in your browser
- Another perl6.org iteration
- Blackjack and Perl 6
- Why I commit Crud to the Perl 6 Test Suite
- This Week's Contribution to Perl 6 Week 5: Implement Str.trans
- This Week's Contribution to Perl 6
- This Week's Contribution to Perl 6 Week 8: Implement $*ARGFILES for Rakudo
- This Week's Contribution to Perl 6 Week 6: Improve Book markup
- This Week's Contribution to Perl 6 Week 2: Fix up a test
- This Week's Contribution to Perl 6 Week 9: Implement Hash.pick for Rakudo
- This Week's Contribution to Perl 6 Week 11: Improve an error message for Hyper Operators
- This Week's Contribution to Perl 6 - Lottery Intermission
- This Week's Contribution to Perl 6 Week 3: Write supporting code for the MAIN sub
- This Week's Contribution to Perl 6 Week 1: A website for proto
- This Week's Contribution to Perl 6 Week 4: Implement :samecase for .subst
- This Week's Contribution to Perl 6 Week 10: Implement samespace for Rakudo
- This Week's Contribution to Perl 6 Week 7: Implement try.rakudo.org
- What is the "Cool" class in Perl 6?
- Report from the Perl 6 Hackathon in Copenhagen
- Custom operators in Rakudo
- A Perl 6 Date Module
- Defined Behaviour with Undefined Values
- Dissecting the "Starry obfu"
- The case for distributed version control systems
- Perl 6: Failing Softly with Unthrown Exceptions
- Perl 6 Compiler Feature Matrix
- The first Perl 6 module on CPAN
- A Foray into Perl 5 land
- Gabor: Keep going
- First Grant Report: Structured Error Messages
- Second Grant Report: Structured Error Messages
- Third Grant Report: Structured Error Messages
- Fourth Grant Report: Structured Error Messages
- Google Summer of Code Mentor Recap
- How core is core?
- How fast is Rakudo's "nom" branch?
- Building a Huffman Tree With Rakudo
- Immutable Sigils and Context
- Is Perl 6 really Perl?
- Mini-Challenge: Write Your Prisoner's Dilemma Strategy
- Longest Palindrome by Regex
- Perl 6: Lost in Wonderland
- Lots of momentum in the Perl 6 community
- Monetize Perl 6?
- Musings on Rakudo's spectest chart
- My first executable from Perl 6
- My first YAPC - YAPC::EU 2010 in Pisa
- Trying to implement new operators - failed
- Programming Languages Are Not Zero Sum
- Perl 6 notes from February 2011
- Notes from the YAPC::EU 2010 Rakudo hackathon
- Let's build an object
- Perl 6 is optimized for fun
- How to get a parse tree for a Perl 6 Program
- Pascal's Triangle in Perl 6
- Perl 6 in 2009
- Perl 6 in 2010
- Perl 6 in 2011 - A Retrospection
- Perl 6 ticket life cycle
- The Perl Survey and Perl 6
- The Perl 6 Advent Calendar
- Perl 6 Questions on Perlmonks
- Physical modeling with Math::Model and Perl 6
- How to Plot a Segment of a Circle with SVG
- Results from the Prisoner's Dilemma Challenge
- Protected Attributes Make No Sense
- Publicity for Perl 6
- PVC - Perl 6 Vocabulary Coach
- Fixing Rakudo Memory Leaks
- Rakudo architectural overview
- Rakudo Rocks
- Rakudo "star" announced
- My personal "I want a PONIE" wish list for Rakudo Star
- Rakudo's rough edges
- Rats and other pets
- The Real World Strikes Back - or why you shouldn't forbid stuff just because you think it's wrong
- Releasing Rakudo made easy
- Set Phasers to Stun!
- Starry Perl 6 obfu
- Recent Perl 6 Developments August 2008
- The State of Regex Modifiers in Rakudo
- Strings and Buffers
- Subroutines vs. Methods - Differences and Commonalities
- A SVG plotting adventure
- A Syntax Highlighter for Perl 6
- Test Suite Reorganization: How to move tests
- The Happiness of Design Convergence
- Thoughts on masak's Perl 6 Coding Contest
- The Three-Fold Function of the Smart Match Operator
- Perl 6 Tidings from September and October 2008
- Perl 6 Tidings for November 2008
- Perl 6 Tidings from December 2008
- Perl 6 Tidings from January 2009
- Perl 6 Tidings from February 2009
- Perl 6 Tidings from March 2009
- Perl 6 Tidings from April 2009
- Perl 6 Tidings from May 2009
- Perl 6 Tidings from May 2009 (second iteration)
- Perl 6 Tidings from June 2009
- Perl 6 Tidings from August 2009
- Perl 6 Tidings from October 2009
- Timeline for a syntax change in Perl 6
- Visualizing match trees
- Want to write shiny SVG graphics with Perl 6? Port Scruffy!
- We write a Perl 6 book for you
- When we reach 100% we did something wrong
- Where Rakudo Lives Now
- Why Rakudo needs NQP
- Why was the Perl 6 Advent Calendar such a Success?
- What you can write in Perl 6 today
- Why you don't need the Y combinator in Perl 6
- You are good enough!
Sun, 27 May 2012
Exceptions Grant Report for May 2012
It seems quite a long time since I started working on my grant on exceptions, and I until quite recently I felt that I still had quite a long way to go. And then I read the deliverables again, and found that I have actually achieved quite a bit of them already. I also noticed that some of them are quite ambiguously formulated.
Also when I wrote the grant application I had a clever system in the back of my mind that lets you categorize exceptions with different tags. After presenting that idea to the #perl6 channel, they uniformly told me that it was a (bad) reinvention of the existing type system. They were right, of course. So instead exceptions use the "real" type system now, which means that some aspects of the grant application do not make so much sense now.
Let's look at the deliverables in detail:
S32::Exception contains my work in this area..
Since exceptions use the normal Perl 6 type system, the amount of work I had to do was less than I had expected. I consider it done, in the sense that everything is there that we need to throw typed exceptions and work with them in a meaningful and intuitive way.
There are certainly still open design question in the general space of exceptions (like, how do we indicate that an exception should or should not print its backtrace by default? There are ways to achieve this right now, but it's not as easy as it it should be for the end user). However those open questions are well outside the realm of this grant. I still plan to tackle them in due time.
D2: Error catalog, tests
The error catalog is compiled and in Rakudo's src/core/Exception.pm. It is not comprehensive (ie doesn't cover all possible errors that are thrown from current compilers), but the grant request only required an "initial" catalog. It is certainly enough to demonstrate the feasibility of the design, and to handle many very common cases. I will certainly summarize it in the S32::Exception document.
Tests are in the roast repository. At the time of writing there are 343 tests (Update 2012-06-04: 411 tests), of which Rakudo passes nearly all (the few failures are due to misparses, which cause wrong parse errors to be generated). They cover both the exceptions API and the individual exception types.
D3: Implementation, tests, documentation
The meat of the implementation is done. Not all exceptions thrown from the setting are typed yet, about 30 remain (plus a few for internal errors that don't make sense to improve much). (Update 2012-06-04: all of these 30 errors now throw typed exceptions too). The tests mentioned above already cover several RT tickets where people complained about wrong or less-than-awesome errors. Documentation is still missing, though I have given a walk through the process of adding a new typed exception to Rakudo on IRC, which might serve as a starting point for such documentation.
So in summary, still missing are
- Finish changing text based exceptions to typed exceptions in CORE
- Documenting the error catalog in S32::Exception
- Documentation for compiler writers and test writers
A surprisingly short list :-)
I'd also like to mention that I did several things related to exceptions which were not covered by this grant report:
- greatly improved backtrace printer
- Many exceptions from within the compilation process (such as parse errors, redeclarations etc.) are now typed.
- I enabled typed exceptions thrown from C code, and as a proof of concept I ported all user-visible exceptions in perl6.ops to their intended types.
- Exceptions from within the meta model can now be caught in the "actions" part of the compiler, augmented with line numbers and file name and re-thrown