Editing Parrot virtual machine (section)

==Languages==
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, and [[data structure]]s between languages.

===Static and dynamic languages===
The differing properties of [[Type checking|statically and dynamically typed]] languages motivated the design of Parrot. Current popular virtual machines such as the [[Java virtual machine]] and the [[Common 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 also [[Stack machine|stack-based]]. Parrot developers chose a register-based design, reasoning that it more closely resembles a hardware design, allowing the vast literature on [[compiler optimization]] to be used in generating bytecode for the Parrot virtual machine that could run at speeds closer to [[machine code]].{{cn|date=November 2023}} Other register-based virtual machines inspired parts of Parrot's design, including [[LLVM]], the [[Lua (programming language)#Internals|Lua VM]] and Inferno's [[Dis virtual machine|Dis]].

==={{Anchor|PMC}}Functional concepts===
Parrot has rich support for several features of [[functional programming]] including [[Closure (computer science)|closures]] and [[continuation]]s, both of which can be particularly difficult to implement correctly and portably, especially in conjunction with [[exception handling]] and [[thread (computer science)|threading]]. The biggest advantage is the dynamic extendability of objects with methods, which allows for ''polymorphic containers'' (PMCs) and associated [[opcode]]s. Implementing solutions to these problems at the virtual machine level obviates the need to solve them in the individual client languages.

===Compiler tools===
{{Main|Parser Grammar Engine}} <!-- note: once [[Parrot compiler toolchain]] exists, that should be the main link -->

Parrot provides a suite of [[Parrot compiler toolchain|compiler-writing tools]]<ref>[http://docs.parrot.org/parrot/latest/html/docs/book/ch04_compiler_tools.pod.html] {{webarchive|url=https://web.archive.org/web/20090509161210/http://docs.parrot.org/parrot/latest/html/docs/book/ch04_compiler_tools.pod.html|date=May 9, 2009}}</ref> which includes the [[Parser Grammar Engine]] (PGE), a hybrid parser-generator that can express a [[recursive descent parser]] as well as an [[operator-precedence parser]], allowing free transition between the two in a single grammar. The PGE feeds into the [[Tree Grammar Engine]] (TGE) which further transforms the parse-tree generated by PGE for optimization and ultimately for code generation.

===Implementations===
The most complete language implementations targeting the Parrot VM were Raku (known at the time as Rakudo Perl 6), [[Lua (programming language)|Lua]] and a new language called "Winxed".<ref>{{cite web|url=http://www.parrot.org/languages|title=Languages - Parrot VM |publisher=parrot.org |access-date=2023-11-18}}</ref> Projects to implement many other languages were started, including [[PHP]], [[Python (programming language)|Python]], and [[Ruby (programming language)|Ruby]]; along with esoteric and demonstration languages such as [[Befunge]] and the "[[Wikibooks:Parrot Virtual Machine/Squaak Tutorial|squaak]]" tutorial language.<ref>{{cite web|url=https://trac.parrot.org/parrot/wiki/Languages |title=Languages – Parrot |publisher=Parrot development wiki |access-date=2023-11-18}}</ref> None of these projects were successful in becoming the primary implementation of their respective languages.<ref name="inactive-parrot" />