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| <div><h2 class="title"> |
| <a name="proto"></a>Chapter 15. Boost.Proto</h2></div> |
| <div><div class="author"><h3 class="author"> |
| <span class="firstname">Eric</span> <span class="surname">Niebler</span> |
| </h3></div></div> |
| <div><p class="copyright">Copyright © 2008 Eric Niebler</p></div> |
| <div><div class="legalnotice"> |
| <a name="id2147997"></a><p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></div> |
| </div></div> |
| <div class="toc"> |
| <p><b>Table of Contents</b></p> |
| <dl> |
| <dt><span class="section"><a href="proto.html#boost_proto.preface">Preface</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html">Users' Guide</a></span></dt> |
| <dd><dl> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.getting_started">Getting Started</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.front_end">Fronts Ends: Defining |
| Terminals and Non-Terminals of Your DSEL</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.intermediate_form">Intermediate |
| Form: Understanding and Introspecting Expressions</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.back_end">Back Ends: Making Expression |
| Templates Do Useful Work</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.examples">Examples</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.resources">Background and Resources</a></span></dt> |
| <dt><span class="section"><a href="proto/users_guide.html#boost_proto.users_guide.glossary">Glossary</a></span></dt> |
| </dl></dd> |
| <dt><span class="section"><a href="proto/reference.html">Reference</a></span></dt> |
| <dd><dl> |
| <dt><span class="section"><a href="proto/reference.html#proto.concepts">Concepts</a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#proto.reference.classes">Classes</a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#proto.reference.functions">Functions</a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.args_hpp">Header <boost/proto/args.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.core_hpp">Header <boost/proto/core.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.debug_hpp">Header <boost/proto/debug.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.deep_copy_hpp">Header <boost/proto/deep_copy.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.domain_hpp">Header <boost/proto/domain.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.eval_hpp">Header <boost/proto/eval.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.expr_hpp">Header <boost/proto/expr.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.extends_hpp">Header <boost/proto/extends.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.fusion_hpp">Header <boost/proto/fusion.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.generate_hpp">Header <boost/proto/generate.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.literal_hpp">Header <boost/proto/literal.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.make_expr_hpp">Header <boost/proto/make_expr.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.matches_hpp">Header <boost/proto/matches.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.operators_hpp">Header <boost/proto/operators.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.proto_hpp">Header <boost/proto/proto.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.proto_fwd_hpp">Header <boost/proto/proto_fwd.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.proto_typeof_hpp">Header <boost/proto/proto_typeof.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.repeat_hpp">Header <boost/proto/repeat.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.tags_hpp">Header <boost/proto/tags.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.traits_hpp">Header <boost/proto/traits.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.arg_hpp">Header <boost/proto/transform/arg.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.call_hpp">Header <boost/proto/transform/call.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.default_hpp">Header <boost/proto/transform/default.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.fold_hpp">Header <boost/proto/transform/fold.hpp></a></span></dt> |
| <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> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.impl_hpp">Header <boost/proto/transform/impl.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.lazy_hpp">Header <boost/proto/transform/lazy.hpp></a></span></dt> |
| <dt><span class="section"><a href="proto/reference.html#header.boost.proto.transform.make_hpp">Header <boost/proto/transform/make.hpp></a></span></dt> |
| <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.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 |
| Notes</a></span></dt> |
| <dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.history">Appendix B: History</a></span></dt> |
| <dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.rationale">Appendix C: Rationale</a></span></dt> |
| <dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.implementation">Appendix D: Implementation |
| Notes</a></span></dt> |
| <dt><span class="section"><a href="proto/appendices.html#boost_proto.appendices.acknowledgements">Appendix E: |
| Acknowledgements</a></span></dt> |
| </dl></dd> |
| </dl> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="boost_proto.preface"></a><a class="link" href="proto.html#boost_proto.preface" title="Preface">Preface</a> |
| </h2></div></div></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <span class="quote">“<span class="quote">There are more things in heaven and earth, Horatio, than are dreamt |
| of in your philosophy.</span>”</span> |
| </p></blockquote></div> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <span class="bold"><strong><span class="emphasis"><em>-- William Shakespeare</em></span></strong></span> |
| </p></blockquote></div> |
| <a name="boost_proto.preface.description"></a><h4> |
| <a name="id2148063"></a> |
| <a class="link" href="proto.html#boost_proto.preface.description">Description</a> |
| </h4> |
| <p> |
| Proto is a framework for building Domain Specific Embedded Languages in C++. |
| It provides tools for constructing, type-checking, transforming and executing |
| <span class="emphasis"><em>expression templates</em></span><sup>[<a name="id2148083" href="#ftn.id2148083" class="footnote">2</a>]</sup>. More specifically, Proto provides: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| An expression tree data structure. |
| </li> |
| <li class="listitem"> |
| A mechanism for giving expressions additional behaviors and members. |
| </li> |
| <li class="listitem"> |
| Operator overloads for building the tree from an expression. |
| </li> |
| <li class="listitem"> |
| Utilities for defining the grammar to which an expression must conform. |
| </li> |
| <li class="listitem"> |
| An extensible mechanism for immediately executing an expression template. |
| </li> |
| <li class="listitem"> |
| An extensible set of tree transformations to apply to expression trees. |
| </li> |
| </ul></div> |
| <a name="boost_proto.preface.motivation"></a><h4> |
| <a name="id2148156"></a> |
| <a class="link" href="proto.html#boost_proto.preface.motivation">Motivation</a> |
| </h4> |
| <p> |
| Expression Templates are an advanced technique that C++ library developers |
| use to define embedded mini-languages that target specific problem domains. |
| The technique has been used to create efficient and easy-to-use libraries for |
| linear algebra as well as to define C++ parser generators with a readable syntax. |
| But developing such a library involves writing an inordinate amount of unreadable |
| and unmaintainable template mumbo-jumbo. Boost.Proto eases the development |
| of <a class="link" href="proto/users_guide.html#boost_proto.users_guide.glossary.dsel">domain-specific embedded |
| languages (DSELs)</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 a DSEL for defining DSELs. |
| </p> |
| <a name="boost_proto.preface.how_to_use_this_documentation"></a><h4> |
| <a name="id2148193"></a> |
| <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" type="disc"> |
| <li class="listitem"> |
| 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>. |
| </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>. |
| </li> |
| <li class="listitem"> |
| Names that refer to <span class="emphasis"><em>concepts</em></span> in the generic programming |
| sense are specified in CamelCase. |
| </li> |
| </ul></div> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../doc/src/images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| In addition, notes such as this one specify non-essential information that |
| provides additional background or rationale. |
| </p></td></tr> |
| </table></div> |
| <p> |
| Finally, you can mentally add the following to any code fragments in this document: |
| </p> |
| <pre class="programlisting"><span class="comment">// Include all of Proto |
| </span><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> |
| |
| <span class="comment">// Create some namespace aliases |
| </span><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> |
| <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> |
| |
| <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 width="100" align="left"> |
| <div class="footnote"><p><sup>[<a name="ftn.id2148083" href="#id2148083" class="para">2</a>] </sup> |
| See <a href="http://www.osl.iu.edu/~tveldhui/papers/Expression-Templates/exprtmpl.html" 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> |
| <td align="left"><p><small>Last revised: November 10, 2010 at 00:45:08 GMT</small></p></td> |
| <td align="right"><div class="copyright-footer"></div></td> |
| </tr></table> |
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