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Joel de Guzman 994d4e48cc moving stuff to classic spirit 
[SVN r44163]
2008-04-10 23:51:31 +00:00

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<title>Organization</title>
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<td width="85%"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Organization</b></font>
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<p>The framework is highly modular and is organized in layers:</p>
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<td><div align="center"><font color="#003366"><strong>iterator</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>actor</strong></font></div></td>
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<td><div align="center"><font color="#003366"><strong>debug</strong></font></div></td>
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<td><div align="center"><font color="#003366"><strong>attribute</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>dynamic</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>error_handling</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>symbols</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>tree</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>utility</strong></font></div></td>
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<td><div align="center"><font color="#003366"><strong>meta</strong></font></div></td>
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<td colspan="4"><div align="center"><font color="#003366"><strong><font size="4">core</font></strong></font></div></td>
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<td><div align="center"><font color="#003366"><strong>scanner</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>primitives</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>composite</strong></font></div></td>
<td><div align="center"><font color="#003366"><strong>non_terminal</strong></font></div></td>
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<p>Spirit has four layers, plus an independent top layer. The independent layer,
comprising of actor and iterator, does not rely on the other layers. The framework's
architecture is completely orthogonal. The relationship among the layers is
acyclic. Lower layers do not depend nor know the existence of upper layers.
Modules in a layer do not depend on other modules in the same layer. </p>
<p>The client may use only the modules that she wants without incurring any compile
time nor run time penalty. A minimalistic approach is to use only the core as
is. The highly streamlined core is usable by itself. The core is sufficiently
suitable for tasks such as micro parsing.</p>
<p>The <strong>iterator</strong> module is independent of Spirit and may be used
in other non-Spirit applications. This module is a compilation of stand-alone
iterators and iterator wrappers compatible with Spirit.
Over time, these iterators have been found to be most useful for parsing with Spirit. </p>
<p>The <strong>actor</strong> module, also independent of Spirit, is a compilation
of predefined semantic actions that covers the most common semantics processing
tasks.</p>
<p>The <strong>debug</strong> module provides library wide parser debugging. This
module hooks itself up transparently into the core non-intrusively and only
when necessary.</p>
<p>The<strong> attribute</strong> module introduces advanced semantic action machinery
with emphasis on extraction and passing of data up and down the parser hierarchy
through inherited and synthesized attributes. Attributes may also be used to
actually control the parsing. Parametric parsers are a form of dynamic parsers
that changes their behavior at run time based on some attribute or data.</p>
<p>The <strong>dynamic</strong> module focuses on parsers with behavior that can
be modified at run-time.</p>
<p><strong>error_handling</strong>. The framework would not be complete without
Error Handling. C++'s exception handling mechanism is a perfect match for Spirit
due to its highly recursive functional nature. C++ Exceptions are used extensively
by this module for handling errors.</p>
<p>The<strong> symbols</strong> module focuses on symbol table management. This module
is rather basic now. The goal is to build a sub-framework that will be able
to accommodate C++ style multiple scope mechanisms. C++ is a great model for
the complexity of scoping that perhaps has no parallel in any other language.
There are classes and inheritance, private, protected and public access restrictions,
friends, namespaces, using declarations, using directives, Koenig lookup (Argument
Dependent Lookup) and more. The symbol table functionality we have now will
be the basis of a complete facility that will attempt to model this.</p>
<blockquote>
<p><em><font color="#003366">I wish that I could ever see, a structure as lovely
as a tree</font></em><font color="#003366">...</font></p>
</blockquote>
<p> Parse Tree and Abstract Syntax Tree (AST) generation are handled by the <b>Tree</b>
module. There are advantages with Parse Trees and Abstract Syntax Trees over
semantic actions. You can make multiple passes over the data without having
to re-parse the input. You can perform transformations on the tree. You can
evaluate things in any order you want, whereas with attribute schemes you have
to process in a begin to end fashion. You do not have to worry about backtracking
and action side effects that may occur with an ambiguous grammar.</p>
<p>The <b>utility</b> module is a set of commonly useful parsers and support classes
that were found to be useful in handling common tasks such as list processing,
comments, confix expressions, etc.</p>
<p><strong>meta</strong>, provides metaprogramming facilities for advanced Spirit
developers. This module facilitates compile-time and run-time introspection
of Spirit parsers.</p>
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<p class="copyright">Copyright &copy; 1998-2003 Joel de Guzman<br>
<br>
<font size="2">Use, modification and distribution is subject to the Boost Software
License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt)</font></p>
<p class="copyright">&nbsp;</p>
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