docs/architecture.html

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    <title>Rakudo architectural overview</title>
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<h1>Rakudo architectural overview</h1>

<p>(This started off <a
href="http://perlgeek.de/blog-en/perl-6/rakudo-overview.html">as a blog
post</a>, which didn't have the fancy clickable SVG image).</p>

<object 
    style="margin:2ex; float:left"
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    alt="Rakudo flow chart"
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<a id="action-methods" />
<h2 id="parser" >Parser and action methods</h2>

<p>The source code is entered at the top of the machine named Rakudo, and is
transformed in various stages. The first two, parser and action methods, are
actually part of Rakudo, and are hosted in the Rakudo repository. They are
written in two different subsets of Perl 6, the regexes (parser), and "Not
Quite Perl 6", short NQP (action methods).</p>

<a id="post-compiler" />
<h2 id="past-compiler">PAST and POST
compiler</h2>

<p>The next two stages (PAST and POST compiler) are part of the so-called
"Parrot Compiler Toolkit", short PCT. Both PAST and POST are structural
representations of the program, with PAST being more high-level than POST.
Both compilers are written in PIR, the parrot
assembly language, and are distributed along with parrot. They are also used
by many other parrot based languages.</p>

<a id="parrot-runloops" />
<h2 id="imcc">IMCC and Parrot runcores</h2>

<p>The POST compiler emits PIR, which IMCC transforms into byte code. IMCC is
parrot's PIR compiler, written in C and statically linked into parrot. The
byte code (PBC) can then be stored to disk, or executed in memory by a
so-called <em>run core</em> or <em>run loop</em>, which is in some sense
the heart
of parrot - or one of the hearts, because there are several different ones
available (one for just-in-time compilation (JIT), one for debugging etc.).</p>

<p>There are also some supporting custom types and operations in Rakudo called
<em>dynamic PMCs</em> and <em>dynamic ops</em> which are written in C, and
helper functions written in other languages (namely NQP and PIR). Those do
not show up in the flow chart.</p>

<h2 id="setting">Setting library</h2>

<p>The part of Rakudo described so far is the <em>stage one</em> compiler.
In the build process it is compiled first, and then it compiles the <em>setting
library</em> down to PBC. "Setting library" is a fancy term describing the
built-in functions which are written in Perl 6. The result of this compilation
(together with a low level runtime library in PIR) is linked together with the
stage one compiler and parrot, the result is the <code>perl6</code>
executable.</p>

<h2 id="glossary">Glossary</h2>

<dl>
    <dt>PGE</dt>
    <dd>Parrot Grammar Engine, parrot's grammar engine for Perl 6 regexes and
        grammars.</dd>

    <dt>NQP</dt>
    <dd>Not Quite Perl 6, a small subset of Perl 6 that is used for tree
        transformations in compilers.</dd>

    <dt>PAST</dt>
    <dd>Parrot Abstract Syntax Tree, an in-memory representation of
        structures common to many programming languages (like variable
        declarations, branches, loops, subroutine calls).</dd>

    <dt>POST</dt>
    <dd>Parrot Opcode Syntax Tree, an in-memory low level representation
        of programs.</dd>

     <dt>PCT</dt>
     <dd>Parrot Compiler Toolkit, a collection of tools and compilers useful
         for writing other compilers.</dd>

     <dt>PIR</dt>
     <dd>Parrot Intermediate Representation, the most commonly used for of
         parrot assembly (which is still high-level enough to be written by
         humans).</dd>

      <dt>IMCC</dt>
      <dd>InterMediate Code Compiler, the part of parrot that compiles PIR
          into byte code.</dd>

       <dt>PBC</dt>
       <dd>Parrot Byte Code, the binary form to which all parrot programs are
           compiled in the end.</dd>
</dl>

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