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 <title>The CommonMark\CQL class</title>
 <titleabbrev>CommonMark\CQL</titleabbrev>

 <partintro>

<!-- {{{ CommonMark\Parser intro -->
  <section xml:id="commonmark-cql.intro">
   &reftitle.intro;
   <para>
    CommonMark Query Language is a DSL for describing how to travel through a CommonMark Node tree implemented as a parser and compiler for a small set of instructions, and a virtual machine for executing those instructions.
   </para>
   <formalpara>
    <title>Paths:</title>
     <para>
      In it's most simplistic form, a CQL query combines the following paths and <literal>/</literal> to describe how to travel through a tree:
      <simplelist>
       <member>firstChild</member>
       <member>lastChild</member>
       <member>previous</member>
       <member>next</member>
       <member>parent</member>
      </simplelist>
      For example, <literal>/firstChild/lastChild</literal> would travel to the last child node of the first child node.
     </para>
   </formalpara>
   <formalpara>
   <title>Loops</title>
   <para>
    CQL can be instructed to loop, for example through the children of, or siblings to a particular node, by using the path <literal>children</literal>, or <literal>siblings</literal>. For example, <literal>/firstChild/children</literal> will travel to all the children of the first child node.
   </para>
   </formalpara>
   <formalpara>
    <title>Subqueries</title>
     <para>
      CQL can be instructed how to travel by using a subquery like <literal>[/firstChild]</literal>. For example, <literal>/firstChild/children[/firstChild]</literal> will travel to the first child node of all the children of the first child node.
     </para>   
   </formalpara>
   <formalpara>
    <title>Loop Constraints</title>
     <para>
      While looping, CQL can be instructed to constrict the travelled path to nodes of particular type. For example <literal>/children(BlockQuote)</literal> will travel to the children of a node where the type is <literal>BlockQuote</literal>. The following types are recognized (case insensitively):
      <simplelist>
       <member>BlockQuote</member>
       <member>List</member>
       <member>Item</member>
       <member>CodeBlock</member>
       <member>HtmlBlock</member>
       <member>CustomBlock</member>
       <member>Paragraph</member>
       <member>Heading</member>
       <member>ThematicBreak</member>
       <member>Text</member>
       <member>SoftBreak</member>
       <member>LineBreak</member>
       <member>Code</member>
       <member>HtmlInline</member>
       <member>CustomInline</member>
       <member>Emphasis</member>
       <member>Strong</member>
       <member>Link</member>
       <member>Image</member>
      </simplelist>
      Types may be used as a union, for example <literal>/children(BlockQuote|List)</literal> will travel to the children of a node where the type is <literal>BlockQuote</literal> or <literal>List</literal>. Types, or unions of types, may be also negated. For example <literal>/children(~BlockQuote)</literal> will travel to the children of a node where the type is not <literal>BlockQuote</literal>, and <literal>/children(~BlockQuote|Paragraph)</literal> will travel to the children of a node where the type is not <literal>BlockQuote</literal> or <literal>Paragraph</literal>
     </para>
   </formalpara>
   <formalpara>
    <title>Path Constraints</title>
     <para>
      CQL can be instructed to create a loop to travel to a node of a particular type, at a particular path. For example, <literal>/firstChild(BlockQuote)</literal> will travel to the first child node where the type is <literal>BlockQuote</literal>. Note that like other loops for <literal>children</literal> and <literal>siblings</literal>, this kind of path can only be followed by a subquery.
     </para>
   </formalpara>
   <formalpara>
    <title>Implementation Notes</title>
    <para>
    While CQL has been implemented as part of the PHP CommonMark extension, it stands separately from PHP and does not use PHP's virtual machine or internal representation of values.
   </para> 
   </formalpara>
  </section>
<!-- }}} -->

  <section xml:id="commonmark-cql.synopsis">
   &reftitle.classsynopsis;

<!-- {{{ Synopsis -->
   <classsynopsis>
    <ooclass><classname>CommonMark\CQL</classname></ooclass>

<!-- {{{ Class synopsis -->
    <classsynopsisinfo>
     <ooclass>
      <classname>CommonMark\CQL</classname>
     </ooclass>
    </classsynopsisinfo>
<!-- }}} -->

    <classsynopsisinfo role="comment">Constructor</classsynopsisinfo>
    <xi:include xpointer="xmlns(db=http://docbook.org/ns/docbook) xpointer(id('commonmark-cql.construct')/db:refsect1[@role='description']/descendant::db:constructorsynopsis[not(@role='procedural')])" />
    
    <classsynopsisinfo role="comment">&Methods;</classsynopsisinfo>
    <xi:include xpointer="xmlns(db=http://docbook.org/ns/docbook) xpointer(id('class.commonmark-cql')/db:refentry/db:refsect1[@role='description']/descendant::db:methodsynopsis[not(@role='procedural')])" />
   </classsynopsis>
<!-- }}} -->

  </section>

 </partintro>

  &reference.cmark.commonmark.cql.construct;
  &reference.cmark.commonmark.cql.invoke;

</phpdoc:classref>

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