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<div><h2 class="title">
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<a name="proto"></a>Chapter 33. Boost.Proto</h2></div>
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<div><div class="author"><h3 class="author">
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<span class="firstname">Eric</span> <span class="surname">Niebler</span>
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</h3></div></div>
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<div><p class="copyright">Copyright © 2008 Eric Niebler</p></div>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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<div class="toc">
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<p><b>Table of Contents</b></p>
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<dl class="toc">
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<dt><span class="section"><a href="proto.html#boost_proto.preface">Preface</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html">Users' Guide</a></span></dt>
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<dd><dl>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.getting_started">Getting Started</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.front_end">Fronts Ends: Defining
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Terminals and Non-Terminals of Your EDSL</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.intermediate_form">Intermediate
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Form: Understanding and Introspecting Expressions</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.back_end">Back Ends: Making Expression
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Templates Do Useful Work</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.examples">Examples</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.resources">Background and Resources</a></span></dt>
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<dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.glossary">Glossary</a></span></dt>
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</dl></dd>
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<dt><span class="section"><a href="proto/reference.html">Reference</a></span></dt>
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<dd><dl>
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<dt><span class="section"><a href="proto/reference.html#proto.concepts">Concepts</a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#proto.reference.classes">Classes</a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#proto.reference.functions">Functions</a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.args_hpp">Header <boost/proto/args.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.core_hpp">Header <boost/proto/core.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.debug_hpp">Header <boost/proto/debug.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.deep_copy_hpp">Header <boost/proto/deep_copy.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.domain_hpp">Header <boost/proto/domain.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.eval_hpp">Header <boost/proto/eval.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.expr_hpp">Header <boost/proto/expr.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.extends_hpp">Header <boost/proto/extends.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional_hpp">Header <boost/proto/functional.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion_hpp">Header <boost/proto/functional/fusion.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion.at_hpp">Header <boost/proto/functional/fusion/at.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion.pop_back_hpp">Header <boost/proto/functional/fusion/pop_back.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion.pop_front_hpp">Header <boost/proto/functional/fusion/pop_front.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion.push_back_hpp">Header <boost/proto/functional/fusion/push_back.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion.push_front_hpp">Header <boost/proto/functional/fusion/push_front.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.fusion.reverse_hpp">Header <boost/proto/functional/fusion/reverse.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.range.begin_hpp">Header <boost/proto/functional/range/begin.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.range.empty_hpp">Header <boost/proto/functional/range/empty.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.range.end_hpp">Header <boost/proto/functional/range/end.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.range.rbegin_hpp">Header <boost/proto/functional/range/rbegin.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.range.rend_hpp">Header <boost/proto/functional/range/rend.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.range.size_hpp">Header <boost/proto/functional/range/size.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.std_hpp">Header <boost/proto/functional/std.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.std.iterator_hpp">Header <boost/proto/functional/std/iterator.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.functional.std.utility_hpp">Header <boost/proto/functional/std/utility.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.fusion_hpp">Header <boost/proto/fusion.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.generate_hpp">Header <boost/proto/generate.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.literal_hpp">Header <boost/proto/literal.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.make_expr_hpp">Header <boost/proto/make_expr.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.matches_hpp">Header <boost/proto/matches.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.operators_hpp">Header <boost/proto/operators.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.proto_hpp">Header <boost/proto/proto.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.proto_fwd_hpp">Header <boost/proto/proto_fwd.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.proto_typeof_hpp">Header <boost/proto/proto_typeof.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.repeat_hpp">Header <boost/proto/repeat.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.tags_hpp">Header <boost/proto/tags.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.traits_hpp">Header <boost/proto/traits.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform_hpp">Header <boost/proto/transform.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.arg_hpp">Header <boost/proto/transform/arg.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.call_hpp">Header <boost/proto/transform/call.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.default_hpp">Header <boost/proto/transform/default.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.env_hpp">Header <boost/proto/transform/env.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.fold_hpp">Header <boost/proto/transform/fold.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.fold_tree_hpp">Header <boost/proto/transform/fold_tree.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.impl_hpp">Header <boost/proto/transform/impl.hpp></a></span></dt>
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.integral_c_hpp">Header <boost/proto/transform/integral_c.hpp></a></span></dt>
|
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.lazy_hpp">Header <boost/proto/transform/lazy.hpp></a></span></dt>
|
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<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.make_hpp">Header <boost/proto/transform/make.hpp></a></span></dt>
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||
<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.pass_through_hpp">Header <boost/proto/transform/pass_through.hpp></a></span></dt>
|
||
<dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.when_hpp">Header <boost/proto/transform/when.hpp></a></span></dt>
|
||
<dt><span class="section"><a href="proto/reference.html#header.boost.proto.context_hpp">Header <boost/proto/context.hpp></a></span></dt>
|
||
<dt><span class="section"><a href="proto/reference.html#header.boost.proto.context.callable_hpp">Header <boost/proto/context/callable.hpp></a></span></dt>
|
||
<dt><span class="section"><a href="proto/reference.html#header.boost.proto.context.default_hpp">Header <boost/proto/context/default.hpp></a></span></dt>
|
||
<dt><span class="section"><a href="proto/reference.html#header.boost.proto.context.null_hpp">Header <boost/proto/context/null.hpp></a></span></dt>
|
||
</dl></dd>
|
||
<dt><span class="section"><a href="proto/appendices.html">Appendices</a></span></dt>
|
||
<dd><dl>
|
||
<dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.release_notes">Appendix A: Release
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Notes</a></span></dt>
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<dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.history">Appendix B: History</a></span></dt>
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||
<dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.rationale">Appendix C: Rationale</a></span></dt>
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<dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.implementation">Appendix D: Implementation
|
||
Notes</a></span></dt>
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<dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.acknowledgements">Appendix E:
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||
Acknowledgements</a></span></dt>
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||
</dl></dd>
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||
</dl>
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||
</div>
|
||
<div class="section">
|
||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="boost_proto.preface"></a><a class="link" href="proto.html#boost_proto.preface" title="Preface">Preface</a>
|
||
</h2></div></div></div>
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||
<div class="blockquote"><blockquote class="blockquote"><p>
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||
<span class="quote">“<span class="quote">There are more things in heaven and earth, Horatio, than are dreamt
|
||
of in your philosophy.</span>”</span>
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||
</p></blockquote></div>
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<div class="blockquote"><blockquote class="blockquote"><p>
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||
<span class="bold"><strong><span class="emphasis"><em>-- William Shakespeare</em></span></strong></span>
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||
</p></blockquote></div>
|
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<h4>
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||
<a name="boost_proto.preface.h0"></a>
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||
<span class="phrase"><a name="boost_proto.preface.description"></a></span><a class="link" href="proto.html#boost_proto.preface.description">Description</a>
|
||
</h4>
|
||
<p>
|
||
Proto is a framework for building Embedded Domain-Specific Languages in C++.
|
||
It provides tools for constructing, type-checking, transforming and executing
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<span class="emphasis"><em>expression templates</em></span><a href="#ftn.boost_proto.preface.f0" class="footnote" name="boost_proto.preface.f0"><sup class="footnote">[33]</sup></a>. More specifically, Proto provides:
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||
</p>
|
||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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||
<li class="listitem">
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||
An expression tree data structure.
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||
</li>
|
||
<li class="listitem">
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||
A mechanism for giving expressions additional behaviors and members.
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||
</li>
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||
<li class="listitem">
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||
Operator overloads for building the tree from an expression.
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||
</li>
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||
<li class="listitem">
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||
Utilities for defining the grammar to which an expression must conform.
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||
</li>
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||
<li class="listitem">
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||
An extensible mechanism for immediately executing an expression template.
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||
</li>
|
||
<li class="listitem">
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||
An extensible set of tree transformations to apply to expression trees.
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||
</li>
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||
</ul></div>
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||
<h4>
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||
<a name="boost_proto.preface.h1"></a>
|
||
<span class="phrase"><a name="boost_proto.preface.motivation"></a></span><a class="link" href="proto.html#boost_proto.preface.motivation">Motivation</a>
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||
</h4>
|
||
<p>
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||
Expression Templates are an advanced technique that C++ library developers
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||
use to define embedded mini-languages that target specific problem domains.
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||
The technique has been used to create efficient and easy-to-use libraries for
|
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linear algebra as well as to define C++ parser generators with a readable syntax.
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||
But developing such a library involves writing an inordinate amount of unreadable
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||
and unmaintainable template mumbo-jumbo. Boost.Proto eases the development
|
||
of <a class="link" href="proto/users_guide.html#boost_proto.users_guide.glossary.edsl">domain-specific embedded
|
||
languages (EDSLs)</a>. Use Proto to define the primitives of your mini-language
|
||
and let Proto handle the operator overloading and the construction of the expression
|
||
parse tree. Immediately evaluate the expression tree by passing it a function
|
||
object. Or transform the expression tree by defining the grammar of your mini-language,
|
||
decorated with an assortment of tree transforms provided by Proto or defined
|
||
by you. Then use the grammar to give your users short and readable syntax errors
|
||
for invalid expressions! No more mumbo-jumbo -- an expression template library
|
||
developed with Proto is declarative and readable.
|
||
</p>
|
||
<p>
|
||
In short, Proto is an EDSL for defining EDSLs.
|
||
</p>
|
||
<h4>
|
||
<a name="boost_proto.preface.h2"></a>
|
||
<span class="phrase"><a name="boost_proto.preface.how_to_use_this_documentation"></a></span><a class="link" href="proto.html#boost_proto.preface.how_to_use_this_documentation">How
|
||
to Use This Documentation</a>
|
||
</h4>
|
||
<p>
|
||
This documentation makes use of the following naming and formatting conventions.
|
||
</p>
|
||
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
|
||
<li class="listitem">
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||
Code is in <code class="computeroutput"><span class="identifier">fixed</span> <span class="identifier">width</span>
|
||
<span class="identifier">font</span></code> and is syntax-highlighted.
|
||
</li>
|
||
<li class="listitem">
|
||
Replaceable text that you will need to supply is in <em class="replaceable"><code>italics</code></em>.
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||
</li>
|
||
<li class="listitem">
|
||
If a name refers to a free function, it is specified like this: <code class="computeroutput"><span class="identifier">free_function</span><span class="special">()</span></code>;
|
||
that is, it is in code font and its name is followed by <code class="computeroutput"><span class="special">()</span></code>
|
||
to indicate that it is a free function.
|
||
</li>
|
||
<li class="listitem">
|
||
If a name refers to a class template, it is specified like this: <code class="computeroutput"><span class="identifier">class_template</span><span class="special"><></span></code>;
|
||
that is, it is in code font and its name is followed by <code class="computeroutput"><span class="special"><></span></code>
|
||
to indicate that it is a class template.
|
||
</li>
|
||
<li class="listitem">
|
||
If a name refers to a function-like macro, it is specified like this:
|
||
<code class="computeroutput"><span class="identifier">MACRO</span><span class="special">()</span></code>;
|
||
that is, it is uppercase in code font and its name is followed by <code class="computeroutput"><span class="special">()</span></code> to indicate that it is a function-like
|
||
macro. Object-like macros appear without the trailing <code class="computeroutput"><span class="special">()</span></code>.
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||
</li>
|
||
<li class="listitem">
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Names that refer to <span class="emphasis"><em>concepts</em></span> in the generic programming
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sense are specified in CamelCase.
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||
</li>
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||
</ul></div>
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||
<div class="note"><table border="0" summary="Note">
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<tr>
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||
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../doc/src/images/note.png"></td>
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||
<th align="left">Note</th>
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||
</tr>
|
||
<tr><td align="left" valign="top"><p>
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||
In addition, notes such as this one specify non-essential information that
|
||
provides additional background or rationale.
|
||
</p></td></tr>
|
||
</table></div>
|
||
<p>
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||
Finally, you can mentally add the following to any code fragments in this document:
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</p>
|
||
<pre class="programlisting"><span class="comment">// Include all of Proto</span>
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||
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">proto</span><span class="special">/</span><span class="identifier">proto</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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||
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||
<span class="comment">// Create some namespace aliases</span>
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||
<span class="keyword">namespace</span> <span class="identifier">mpl</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mpl</span><span class="special">;</span>
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<span class="keyword">namespace</span> <span class="identifier">fusion</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">fusion</span><span class="special">;</span>
|
||
<span class="keyword">namespace</span> <span class="identifier">proto</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">proto</span><span class="special">;</span>
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||
|
||
<span class="comment">// Allow unqualified use of Proto's wildcard pattern</span>
|
||
<span class="keyword">using</span> <span class="identifier">proto</span><span class="special">::</span><span class="identifier">_</span><span class="special">;</span>
|
||
</pre>
|
||
</div>
|
||
<div class="footnotes">
|
||
<br><hr style="width:100; text-align:left;margin-left: 0">
|
||
<div id="ftn.boost_proto.preface.f0" class="footnote"><p><a href="#boost_proto.preface.f0" class="para"><sup class="para">[33] </sup></a>
|
||
See <a href="http://en.wikipedia.org/wiki/Expression_templates" target="_top">Expression
|
||
Templates</a>
|
||
</p></div>
|
||
</div>
|
||
</div>
|
||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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||
<td align="left"><p><small>Last revised: April 13, 2021 at 16:32:31 GMT</small></p></td>
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