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- </div>
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- <div class="titlepage"><div><div><h4 class="title">
- <a name="spirit_repository.karma_components.nonterminal.subrule"></a><a class="link" href="subrule.html" title="Karma subrules">Karma
- subrules</a>
- </h4></div></div></div>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h0"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.description"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.description">Description</a>
- </h6>
- <p>
- The <span class="emphasis"><em>Spirit.Karma</em></span> <code class="computeroutput"><span class="identifier">subrule</span></code>
- is a component allowing to create a named generator, and to refer to it
- by name -- much like rules and grammars. It is in fact a fully static version
- of the rule.
- </p>
- <p>
- The strength of subrules is performance. Replacing some rules with subrules
- can make a generator slightly faster (see <a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.performance">Performance</a>
- below for measurements). The reason is that subrules allow aggressive inlining
- by the C++ compiler, whereas the implementation of rules is based on a
- virtual function call which, depending on the compiler, can have some run-time
- overhead and stop inlining.
- </p>
- <p>
- The weaknesses of subrules are:
- </p>
- <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
- <li class="listitem">
- subrules can only be defined and used within the same generator expression.
- A subrule cannot be defined at one location, and then used in another
- location.
- </li>
- <li class="listitem">
- subrules put a massive strain on the C++ compiler. They increase compile
- times and memory usage during compilation, and also increase the risk
- of hitting compiler limits and/or bugs.
- </li>
- </ul></div>
- <p>
- </p>
- <pre class="programlisting"><span class="identifier">entry</span> <span class="special">%=</span> <span class="special">(</span>
- <span class="identifier">ast_node</span> <span class="special">%=</span> <span class="identifier">int_</span> <span class="special">|</span> <span class="identifier">binary_node</span> <span class="special">|</span> <span class="identifier">unary_node</span>
- <span class="special">,</span> <span class="identifier">binary_node</span> <span class="special">%=</span> <span class="char">'('</span> <span class="special"><<</span> <span class="identifier">ast_node</span> <span class="special"><<</span> <span class="identifier">char_</span> <span class="special"><<</span> <span class="identifier">ast_node</span> <span class="special"><<</span> <span class="char">')'</span>
- <span class="special">,</span> <span class="identifier">unary_node</span> <span class="special">%=</span> <span class="char">'('</span> <span class="special"><<</span> <span class="identifier">char_</span> <span class="special"><<</span> <span class="identifier">ast_node</span> <span class="special"><<</span> <span class="char">')'</span>
- <span class="special">);</span>
- </pre>
- <p>
- </p>
- <p>
- The example above can be found here: <a href="../../../../../example/karma/calc2_ast_dump_sr.cpp" target="_top">../../example/karma/calc2_ast_dump_sr.cpp</a>
- </p>
- <p>
- As shown in this code snippet (an extract from the calc2_ast_dump_sr example),
- subrules can be freely mixed with rules and grammars. Here, a group of
- 3 subrules (<code class="computeroutput"><span class="identifier">ast_node</span></code>,
- <code class="computeroutput"><span class="identifier">binary_node</span></code>, <code class="computeroutput"><span class="identifier">unary_node</span></code>) is assigned to a rule (named
- <code class="computeroutput"><span class="identifier">entry</span></code>). This means that
- parts of a generator can use subrules (typically the innermost, most performance-critical
- parts), whereas the rest can use rules and grammars.
- </p>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h1"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.header"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.header">Header</a>
- </h6>
- <pre class="programlisting"><span class="comment">// forwards to <boost/spirit/repository/home/karma/nonterminal/subrule.hpp></span>
- <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">repository</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma_subrule</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- </pre>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h2"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.synopsis__declaration_"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.synopsis__declaration_">Synopsis
- (declaration)</a>
- </h6>
- <pre class="programlisting"><span class="identifier">subrule</span><span class="special"><</span><span class="identifier">ID</span><span class="special">,</span> <span class="identifier">A1</span><span class="special">,</span> <span class="identifier">A2</span><span class="special">></span> <span class="identifier">sr</span><span class="special">(</span><span class="identifier">name</span><span class="special">);</span>
- </pre>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h3"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.parameters__declaration_"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.parameters__declaration_">Parameters
- (declaration)</a>
- </h6>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Parameter
- </p>
- </th>
- <th>
- <p>
- Description
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">ID</span></code>
- </p>
- </td>
- <td>
- <p>
- Required numeric argument. Gives the subrule a unique 'identification
- tag'.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">A1</span></code>, <code class="computeroutput"><span class="identifier">A2</span></code>
- </p>
- </td>
- <td>
- <p>
- Optional types, can be specified in any order. Can be one of
- 1. signature, 2. locals (see rules reference for more information
- on those parameters).
- </p>
- <p>
- Note that the delimiter type need not be specified in the parameters,
- unlike with grammars and rules. Subrules will automatically use
- the delimiter type which is in effect when they are invoked.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">name</span></code>
- </p>
- </td>
- <td>
- <p>
- Optional string. Gives the subrule a name, useful for debugging
- and error handling.
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h4"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.synopsis__usage_"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.synopsis__usage_">Synopsis
- (usage)</a>
- </h6>
- <p>
- Subrules are defined and used within groups, typically (and by convention)
- enclosed inside parentheses.
- </p>
- <pre class="programlisting"><span class="comment">// Group containing N subrules</span>
- <span class="special">(</span>
- <span class="identifier">sr1</span> <span class="special">=</span> <span class="identifier">expr1</span>
- <span class="special">,</span> <span class="identifier">sr2</span> <span class="special">=</span> <span class="identifier">expr2</span>
- <span class="special">,</span> <span class="special">...</span> <span class="comment">// Any number of subrules</span>
- <span class="special">}</span>
- </pre>
- <p>
- The IDs of all subrules defined within the same group must be different.
- It is an error to define several subrules with the same ID (or to define
- the same subrule multiple times) in the same group.
- </p>
- <pre class="programlisting"><span class="comment">// Auto-subrules and inherited attributes</span>
- <span class="special">(</span>
- <span class="identifier">srA</span> <span class="special">%=</span> <span class="identifier">exprA</span> <span class="special"><<</span> <span class="identifier">srB</span> <span class="special"><<</span> <span class="identifier">srC</span><span class="special">(</span><span class="identifier">c1</span><span class="special">,</span> <span class="identifier">c2</span><span class="special">,</span> <span class="special">...)</span> <span class="comment">// Arguments to subrule srC</span>
- <span class="special">,</span> <span class="identifier">srB</span> <span class="special">%=</span> <span class="identifier">exprB</span>
- <span class="special">,</span> <span class="identifier">srC</span> <span class="special">=</span> <span class="identifier">exprC</span>
- <span class="special">,</span> <span class="special">...</span>
- <span class="special">)(</span><span class="identifier">a1</span><span class="special">,</span> <span class="identifier">a2</span><span class="special">,</span> <span class="special">...)</span> <span class="comment">// Arguments to group, i.e. to start subrule srA</span>
- </pre>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h5"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.parameters__usage_"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.parameters__usage_">Parameters
- (usage)</a>
- </h6>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Parameter
- </p>
- </th>
- <th>
- <p>
- Description
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">sr1</span></code>, <code class="computeroutput"><span class="identifier">sr2</span></code>
- </p>
- </td>
- <td>
- <p>
- Subrules with different IDs.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">expr1</span></code>, <code class="computeroutput"><span class="identifier">expr2</span></code>
- </p>
- </td>
- <td>
- <p>
- Generator expressions. Can include <code class="computeroutput"><span class="identifier">sr1</span></code>
- and <code class="computeroutput"><span class="identifier">sr2</span></code>, as well
- as any other valid generator expressions.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">srA</span></code>
- </p>
- </td>
- <td>
- <p>
- Subrule with a synthesized attribute and inherited attributes.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">srB</span></code>
- </p>
- </td>
- <td>
- <p>
- Subrule with a synthesized attribute.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">srC</span></code>
- </p>
- </td>
- <td>
- <p>
- Subrule with inherited attributes.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">exprA</span></code>, <code class="computeroutput"><span class="identifier">exprB</span></code>, <code class="computeroutput"><span class="identifier">exprC</span></code>
- </p>
- </td>
- <td>
- <p>
- Generator expressions.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">a1</span></code>, <code class="computeroutput"><span class="identifier">a2</span></code>
- </p>
- </td>
- <td>
- <p>
- Arguments passed to the subrule group. They are passed as inherited
- attributes to the group's start subrule, <code class="computeroutput"><span class="identifier">srA</span></code>.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">c1</span></code>, <code class="computeroutput"><span class="identifier">c2</span></code>
- </p>
- </td>
- <td>
- <p>
- Arguments passed as inherited attributes to subrule <code class="computeroutput"><span class="identifier">srC</span></code>.
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h6"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.groups"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.groups">Groups</a>
- </h6>
- <p>
- A subrule group (a set of subrule definitions) is a generator, which can
- be used anywhere in a generator expression (in assignments to rules, as
- well as directly in arguments to functions such as <code class="computeroutput"><span class="identifier">generate</span></code>).
- In a group, generation proceeds from the start subrule, which is the first
- (topmost) subrule defined in that group. In the two groups in the synopsis
- above, <code class="computeroutput"><span class="identifier">sr1</span></code> and <code class="computeroutput"><span class="identifier">srA</span></code> are the start subrules respectively
- -- for example when the first subrule group is called forth, the <code class="computeroutput"><span class="identifier">sr1</span></code> subrule is called.
- </p>
- <p>
- A subrule can only be used in a group which defines it. Groups can be viewed
- as scopes: a definition of a subrule is limited to its enclosing group.
- </p>
- <pre class="programlisting"><span class="identifier">rule</span><span class="special"><</span><span class="identifier">outiter_type</span><span class="special">></span> <span class="identifier">r1</span><span class="special">,</span> <span class="identifier">r2</span><span class="special">,</span> <span class="identifier">r3</span><span class="special">;</span>
- <span class="identifier">subrule</span><span class="special"><</span><span class="number">1</span><span class="special">></span> <span class="identifier">sr1</span><span class="special">;</span>
- <span class="identifier">subrule</span><span class="special"><</span><span class="number">2</span><span class="special">></span> <span class="identifier">sr2</span><span class="special">;</span>
- <span class="identifier">r1</span> <span class="special">=</span>
- <span class="special">(</span> <span class="identifier">sr1</span> <span class="special">=</span> <span class="char">'a'</span> <span class="special"><<</span> <span class="identifier">space</span> <span class="special">)</span> <span class="comment">// First group in r1.</span>
- <span class="special"><<</span> <span class="special">(</span> <span class="identifier">sr2</span> <span class="special">=</span> <span class="special">+</span><span class="identifier">sr1</span> <span class="special">)</span> <span class="comment">// Second group in r1.</span>
- <span class="comment">// ^^^</span>
- <span class="comment">// DOES NOT COMPILE: sr1 is not defined in this</span>
- <span class="comment">// second group, it cannot be used here (its</span>
- <span class="comment">// previous definition is out of scope).</span>
- <span class="special">;</span>
- <span class="identifier">r2</span> <span class="special">=</span>
- <span class="special">(</span> <span class="identifier">sr1</span> <span class="special">=</span> <span class="char">'a'</span> <span class="special"><<</span> <span class="identifier">space</span> <span class="special">)</span> <span class="comment">// Only group in r2.</span>
- <span class="special"><<</span> <span class="identifier">sr1</span>
- <span class="comment">// ^^^</span>
- <span class="comment">// DOES NOT COMPILE: not in a subrule group,</span>
- <span class="comment">// sr1 cannot be used here (here too, its</span>
- <span class="comment">// previous definition is out of scope).</span>
- <span class="special">;</span>
- <span class="identifier">r3</span> <span class="special">=</span>
- <span class="special">(</span> <span class="identifier">sr1</span> <span class="special">=</span> <span class="identifier">space</span> <span class="special"><<</span> <span class="char">'x'</span> <span class="special">)</span> <span class="comment">// Another group. The same subrule `sr1`</span>
- <span class="comment">// can have another, independent</span>
- <span class="comment">// definition in this group.</span>
- <span class="special">;</span>
- </pre>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h7"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.attributes"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.attributes">Attributes</a>
- </h6>
- <p>
- A subrule has the same behavior as a rule with respect to attributes. In
- particular:
- </p>
- <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
- <li class="listitem">
- the type of its synthesized attribute is the one specified in the subrule's
- signature, if any. Otherwise it is <code class="computeroutput"><span class="identifier">unused_type</span></code>.
- </li>
- <li class="listitem">
- the types of its inherited attributes are the ones specified in the
- subrule's signature, if any. Otherwise the subrule has no inherited
- attributes.
- </li>
- <li class="listitem">
- an auto-subrule can be defined by assigning it with the <code class="computeroutput"><span class="special">%=</span></code> syntax. In this case, the subrule's
- synthesized attribute is automatically propagated to the RHS generator's
- attribute.
- </li>
- <li class="listitem">
- the Phoenix placeholders <code class="computeroutput"><span class="identifier">_val</span></code>,
- <code class="computeroutput"><span class="identifier">_r1</span></code>, <code class="computeroutput"><span class="identifier">_r2</span></code>, ... are available to refer to
- the subrule's synthesized and inherited attributes, if present.
- </li>
- </ul></div>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h8"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.locals"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.locals">Locals</a>
- </h6>
- <p>
- A subrule has the same behavior as a rule with respect to locals. In particular,
- the Phoenix placeholders <code class="computeroutput"><span class="identifier">_a</span></code>,
- <code class="computeroutput"><span class="identifier">_b</span></code>, ... are available to
- refer to the subrule's locals, if present.
- </p>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h9"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.example"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.example">Example</a>
- </h6>
- <p>
- Some includes:
- </p>
- <p>
- </p>
- <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">repository</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma_subrule</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">phoenix_core</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">phoenix_operator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">phoenix_fusion</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- </pre>
- <p>
- </p>
- <p>
- Some using declarations:
- </p>
- <p>
- </p>
- <pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">;</span>
- <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">ascii</span><span class="special">;</span>
- <span class="keyword">namespace</span> <span class="identifier">repo</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">repository</span><span class="special">;</span>
- </pre>
- <p>
- </p>
- <p>
- A grammar containing only one rule, defined with a group of 2 subrules:
- </p>
- <p>
- </p>
- <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">mini_xml_generator</span>
- <span class="special">:</span> <span class="identifier">karma</span><span class="special">::</span><span class="identifier">grammar</span><span class="special"><</span><span class="identifier">OutputIterator</span><span class="special">,</span> <span class="identifier">mini_xml</span><span class="special">()></span>
- <span class="special">{</span>
- <span class="identifier">mini_xml_generator</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">mini_xml_generator</span><span class="special">::</span><span class="identifier">base_type</span><span class="special">(</span><span class="identifier">entry</span><span class="special">)</span>
- <span class="special">{</span>
- <span class="identifier">entry</span> <span class="special">%=</span> <span class="special">(</span>
- <span class="identifier">xml</span> <span class="special">=</span>
- <span class="char">'<'</span> <span class="special"><<</span> <span class="identifier">string</span><span class="special">[</span><span class="identifier">_1</span> <span class="special">=</span> <span class="identifier">at_c</span><span class="special"><</span><span class="number">0</span><span class="special">>(</span><span class="identifier">_val</span><span class="special">)]</span> <span class="special"><<</span> <span class="char">'>'</span>
- <span class="special"><<</span> <span class="special">(*</span><span class="identifier">node</span><span class="special">)[</span><span class="identifier">_1</span> <span class="special">=</span> <span class="identifier">at_c</span><span class="special"><</span><span class="number">1</span><span class="special">>(</span><span class="identifier">_val</span><span class="special">)]</span>
- <span class="special"><<</span> <span class="string">"</"</span> <span class="special"><<</span> <span class="identifier">string</span><span class="special">[</span><span class="identifier">_1</span> <span class="special">=</span> <span class="identifier">at_c</span><span class="special"><</span><span class="number">0</span><span class="special">>(</span><span class="identifier">_val</span><span class="special">)]</span> <span class="special"><<</span> <span class="char">'>'</span>
- <span class="special">,</span> <span class="identifier">node</span> <span class="special">%=</span> <span class="identifier">string</span> <span class="special">|</span> <span class="identifier">xml</span>
- <span class="special">);</span>
- <span class="special">}</span>
- <span class="identifier">karma</span><span class="special">::</span><span class="identifier">rule</span><span class="special"><</span><span class="identifier">OutputIterator</span><span class="special">,</span> <span class="identifier">mini_xml</span><span class="special">()></span> <span class="identifier">entry</span><span class="special">;</span>
- <span class="identifier">repo</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">subrule</span><span class="special"><</span><span class="number">0</span><span class="special">,</span> <span class="identifier">mini_xml</span><span class="special">()></span> <span class="identifier">xml</span><span class="special">;</span>
- <span class="identifier">repo</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">subrule</span><span class="special"><</span><span class="number">1</span><span class="special">,</span> <span class="identifier">mini_xml_node</span><span class="special">()></span> <span class="identifier">node</span><span class="special">;</span>
- <span class="special">};</span>
- </pre>
- <p>
- </p>
- <p>
- The definitions of the <code class="computeroutput"><span class="identifier">mini_xml</span></code>
- and <code class="computeroutput"><span class="identifier">mini_xml_node</span></code> data
- structures are not shown here. The full example above can be found here:
- <a href="../../../../../example/karma/mini_xml_karma_sr.cpp" target="_top">../../example/karma/mini_xml_karma_sr.cpp</a>
- </p>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h10"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.performance"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.performance">Performance</a>
- </h6>
- <p>
- For comparison of run-time and compile-time performance when using subrules,
- please see the <a class="link" href="../../qi_components/nonterminal/subrule.html#spirit_repository.qi_components.nonterminal.subrule.performance">Performance</a>
- section of <span class="emphasis"><em>Spirit.Qi</em></span> subrules (the implementation
- of <span class="emphasis"><em>Spirit.Karma</em></span> and <span class="emphasis"><em>Spirit.Qi</em></span>
- subrules is very similar, so performance is very similar too).
- </p>
- <h6>
- <a name="spirit_repository.karma_components.nonterminal.subrule.h11"></a>
- <span class="phrase"><a name="spirit_repository.karma_components.nonterminal.subrule.notes"></a></span><a class="link" href="subrule.html#spirit_repository.karma_components.nonterminal.subrule.notes">Notes</a>
- </h6>
- <p>
- Subrules push the C++ compiler hard. A group of subrules is a single C++
- expression. Current C++ compilers cannot handle very complex expressions
- very well. One restricting factor is the typical compiler's limit on template
- recursion depth. Some, but not all, compilers allow this limit to be configured.
- </p>
- <p>
- g++'s maximum can be set using a compiler flag: <code class="computeroutput"><span class="special">-</span><span class="identifier">ftemplate</span><span class="special">-</span><span class="identifier">depth</span></code>. Set this appropriately if you
- use relatively complex subrules.
- </p>
- </div>
- <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
- <td align="left"></td>
- <td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<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></td>
- </tr></table>
- <hr>
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