 | This article needs to beupdated. Please help update this article to reflect recent events or newly available information.(August 2022) |
| Parrot virtual machine | |
|---|---|
 | |
| Final release | |
| Repository | |
| Written in | C |
| Operating system | Cross-platform |
| Successor | MoarVM (for Raku) |
| Type | Virtual machine |
| License | Artistic License 2.0 |
| Website | www |
Parrot is a discontinuedregister-basedprocess virtual machine designed to rundynamic languages efficiently. It is possible to compileParrot assembly language andParrot intermediate representation (PIR, an intermediate language) to Parrotbytecode and execute it. Parrot isfree andopen-source software.[2]
Parrot was started by thePerl community and developed with help from theopen-source and free software communities. As a result, it was focused onlicense compatibility with Perl (Artistic License 2.0), platform compatibility across a broad array of systems, processor architecture compatibility across most modern processors, speed of execution, small size (around 700k depending on platform), and the flexibility to handle the varying demands made byRaku and other moderndynamic languages.
Version 1.0, with a stableapplication programming interface (API) for development, was released on March 17, 2009.[3] The last version is release 8.1.0 "Andean Parakeet".[1] Parrot was officially discontinued in August 2021, after being supplanted byMoarVM in its main use (Raku) and never becoming a mainstream VM for any of its other supported languages.[4]
The nameParrot came from anApril Fool's joke which announced a hypothetical language, namedParrot, that would unifyPython andPerl.[5][6] The name was later adopted by the Parrot project (initially a part of the Raku development effort) which aimed to support Raku, Python, and other programming languages.
The Parrot Foundation was dissolved in 2014.[7] The Foundation was created in 2008 to hold thecopyright andtrademarks of the Parrot project, to help drive development oflanguage implementations and the core codebase, to provide a base for growing the Parrot community, and to reach out to other language communities.[8]
Historical design decisions are documented in the form of Parrot Design Documents, or PDDs, in the Parrot repository.[9]
Until late 2005,Dan Sugalski was the lead designer and chief architect of Parrot.Chip Salzenberg, a longtime Perl, Linux kernel, and C++ hacker, took over until mid-2006, when he became the lead developer.Allison Randal, the lead developer ofPunie and chief architect of Parrot's compiler tools, was the chief architect until mid-October 2010 when she stepped down and chose Christoph Otto as the new chief architect.[10]
The goal of the Parrot virtual machine was to host client languages and allow inter-operation between them. Several hurdles exist in accomplishing this goal, in particular the difficulty of mapping high-level concepts, data, anddata structures between languages.
The differing properties ofstatically and dynamically typed languages motivated the design of Parrot. Current popular virtual machines such as theJava virtual machine and theCommon Language Runtime (for the.NET platform) have been designed for statically typed languages, while the languages targeted by Parrot are dynamically typed.
Virtual machines such as the Java virtual machine and the current Perl 5 virtual machine are alsostack-based. Parrot developers chose a register-based design, reasoning that it more closely resembles a hardware design, allowing the vast literature oncompiler optimization to be used in generating bytecode for the Parrot virtual machine that could run at speeds closer tomachine code.[citation needed] Other register-based virtual machines inspired parts of Parrot's design, includingLLVM, theLua VM and Inferno'sDis.
Parrot has rich support for several features offunctional programming includingclosures andcontinuations, both of which can be particularly difficult to implement correctly and portably, especially in conjunction withexception handling andthreading. The biggest advantage is the dynamic extendability of objects with methods, which allows forpolymorphic containers (PMCs) and associatedopcodes. Implementing solutions to these problems at the virtual machine level obviates the need to solve them in the individual client languages.
Parrot provides a suite ofcompiler-writing tools[11] which includes theParser Grammar Engine (PGE), a hybrid parser-generator that can express arecursive descent parser as well as anoperator-precedence parser, allowing free transition between the two in a single grammar. The PGE feeds into theTree Grammar Engine (TGE) which further transforms the parse-tree generated by PGE for optimization and ultimately for code generation.
The most complete language implementations targeting the Parrot VM wereRaku (known at the time as Rakudo Perl 6),Lua andWinxed.[12] Projects to implement many other languages were started, includingPHP,Python, andRuby; along with esoteric and demonstration languages such asBefunge and the "squaak" tutorial language.[13] None of these projects were successful in becoming the primary implementation of their respective languages.[4]
There are three forms of program code for Parrot:
Parrot is register-based like most hardwareCPUs, and unlike most virtual machines, which are stack-based. Parrot provides four types of registers:
Parrot provides an arbitrary number of registers; this number is fixed at compile time per subroutine.
In PASM
setI1,4incI1# I1 is now 5addI1,2# I1 is now 7setN1,42.0decN1# N1 is now 41.0subN1,2.0# N1 is now 39.0printI1print','printN1print"\n"end
In PIR
.sub'main' :main$I1 =4inc$I1# $I1 is now 5$I1 +=2# $I1 is now 7$N1 =42.0dec$N1# $N1 is now 41.0$N1 -=2.0# $N1 now 39.0print$I1print', 'print$N1print"\n" .end
mod_parrot is an optional module for theApache web server. It embeds a Parrot virtual machine interpreter into the Apache server and provides access to the Apache API to allow handlers to be written inParrot assembly language, or any high-level language targeted to Parrot.
