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
- A small regex optimization for NQP and Rakudo
- Pattern Matching and Unpacking
- Rakudo's Abstract Syntax Tree
- The REPL trick
- First day at YAPC::Europe 2013 in Kiev
- YAPC Europe 2013 Day 2
- YAPC Europe 2013 Day 3
- A new Perl 6 community server - call for funding
- New Perl 6 community server now live, accepting signups
- A new Perl 6 community server - update
- All Perl 6 modules in a box
- doc.perl6.org: some stats, future directions
- Profiling Perl 6 code on IRC
- Why is it hard to write a compiler for Perl 6?
- Writing docs helps you take the user's perspective
- 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!
Wed, 24 Aug 2011
Why Rakudo needs NQP
Reading through a recent ramble by chromatic, I felt like he said "Rakudo needs NQP to be able to ditch Parrot, once NQP runs on a different platform" (NQP is the "another layer", which sits between Rakudo and Parrot, mentioned in the next-to-final paragraph).
I'm sure chromatic knows that VM independence is the least important reason for having NQP at all, but the casual reader might not, so let me explain the real importance of NQP for Rakudo here.
The short version is just a single word: bootstrapping.
The longer version is that large parts of Rakudo are written in Perl 6 itself (or a subset thereof), and something is needed to break the circularity.
In particular the base of the compiler is written in a subset of Perl 6, and NQP compiles those parts to bytecode, which can then compile the rest of the compiler.
This is not just because we have a fancy for Perl 6, and thus want to write as much of the code in Perl 6, but there are solid technical reasons for writing the compiler in Perl 6.
In Perl 6, the boundary between run time and compile time is blurred, as well as the boundary between the compiler, the run time library and user-space code. For example you alter the grammar with which your source code is parsed, by injecting your own grammar rules.
"Your own grammar rules" above refers to user-space code, while the grammar that is being altered is part of the compiler. If we had written the compiler in something else than Perl 6 (for example Java), it would be horribly difficult to inject user-space Perl 6 code into compiled code from a different language.
And the code not only needs to be injected, but the data passed back and forth between the compiler and the user space need to be Perl 6 objects, so all important data structures in the compiler need to be Perl 6 based anyway.
And it's not just for grammar modifications: At its heart, Perl 6 is an object oriented language. When the compiler sees a class definition, it translates them to a series of method calls on the metaobject, which again needs to be a Perl 6 object, otherwise it wouldn't be easily usable and extensible from the user space.
Now you might think that grammar modifications and changes to the
Metaobject are pretty obscure features, and you could get along just fine
with an incomplete Perl 6 compiler that neglected those two areas. But even
then you'd have lots of interactions between run time and compile time. For
example consider a numeric literal like
42. Obviously that needs
to be constructed of type
Int. What's less obvious is that it
needs to be constructed to be of type Int at compile time already, because
Perl 6 code can run interleaved with the compilation. So the compiler needs to
be able to handle Perl 6 objects in all their generality, which is a huge pain
if the compiler is not written in Perl 6.
Rakudo has cheated on that front in the past, and consequently has had lots of bugs and limitations due to non-Perl 6 objects leaking out at unexpected ends. If you ever got a "Null PMC Access" from Rakudo, you know what I mean.
The lesson we learned was that you need a Perl 6 compiler to implement a Perl 6 compiler, even if that first Perl 6 compiler can handle only a rather limited subset of Perl 6.
And there are also quite some benefits to this approach. For example NQP's new regex engine is implemented as a role in NQP. It is mixed into an NQP class which allows us to build Rakudo, but it is also mixed in a Perl 6 class, which allows the generation of Perl 6-level Match objects without any need to create NQP-level match objects first, and then wrap them in Perl 6 Match objects.
That's what NQP does for us. It allows us to actually write a Perl 6 compiler.
Comments / Trackbacks:
Write a comment