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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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<p> The Spirit is currently organized in basically two layers, the core and all
the modules above the core: Debug, Attribute, Symbols, Tree, Utility and Error
Handling. In the future, new layers may be built on top of existing layers.
The framework's architecture is completely orthogonal. The relationship between
the layers is totally acyclic. The core does not depend nor know the existence
of the other 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 highly suitable
for tasks such as micro parsing.</p>
<p>The <b>Debug</b> module provides library wide parser debugging functionalities.
This module essentially hooks itself up transparently into the core unintrusively
and only when necessary.</p>
<p><b>Attribute</b> 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 change its behavior at run time based on some attribute or data.</p>
<p><b>Symbols</b> module focuses on symbol table management. This module is rather
basic as of 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 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 that were found
to be quite useful. This library of parsers significantly reduce the development
time. There are parsers that handle common tasks such as list processing, comments,
confix expressions, etc.</p>
<p>The framework would not be complete without <b>Error Handling</b>. C++'s exception
handling mechanism is a perfect match for Spirit due to its highly recursive
<em>functional</em> nature. C++ Exceptions are used extensively by this module
for handling errors.</p>
<p>The <b>Iterator</b> module is independent of Spirit and may be used in other
contexts as well. This module is a compilation of stand-alone iterators and
iterator wrappers compatible with Spirit. Over the course of time, these iterators
were found to be most useful for parsing with Spirit. <br>
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<p class="copyright">Copyright © 1998-2002 Joel de Guzman<br>
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