| <html><head><META http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Comparisons</title><link href="book.css" rel="stylesheet" type="text/css"><link href="../book.css" rel="stylesheet" type="text/css"><meta content="DocBook XSL Stylesheets V1.74.0" name="generator"><link rel="home" href="index.html" title="XPath 2.0 Processor User Manual"><link rel="up" href="ch02s03.html" title="How to use the XPath 2.0 grammar with PsychoPath"><link rel="prev" href="ch02s03s06.html" title="Range expressions"><link rel="next" href="ch02s03s08.html" title="Conditional Expressions"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="Comparisons"></a>Comparisons</h3></div></div></div><p>The simplest comparison operators are <span class="bold"><strong>eq</strong></span>, <span class="bold"><strong>ne</strong></span>, |
| <span class="bold"><strong>lt</strong></span>, <span class="bold"><strong>le</strong></span>, <span class="bold"><strong>gt</strong></span>, |
| <span class="bold"><strong>ge</strong></span>. These compare two atomic values |
| of the same type, for example two integers, two dates, or two strings. |
| (Collation hasn’t been implemented in current version of PsychoPath). |
| If the operands are not atomic values, an error is raised.</p><p>The operators <span class="bold"><strong>=''', </strong></span>!=' |
| <span class="italic">, '</span><=' <span class="italic">, |
| '</span>> <span class="bold"><strong>, '''<</strong></span>, and |
| <span class="bold"><strong>>=</strong></span> can compare arbitrary |
| sequences. The result is true if any pair of items from the two |
| sequences has the specified relationship, for example <span class="italic">$A = $B</span> is true if there is an item in |
| <span class="italic">$A</span> that is equal to some item in |
| <span class="italic">$B</span>.</p><p>The operators <span class="bold"><strong>is</strong></span> and <span class="bold"><strong>isnot</strong></span> test whether the operands represent the |
| same (identical) node. For example, <span class="italic">title |
| <a class="ulink" href="1" target="_top">1</a> is * <a class="ulink" href="@note" target="_top">@note</a> <a class="ulink" href="1" target="_top">1</a> </span> is true if the first title child is the |
| first child element that has a <span class="italic">@note</span> attribute. If either operand is an |
| empty sequence the result is an empty sequence (which will usually be |
| treated as false).</p><p>The operators <span class="bold"><strong><<</strong></span> and |
| <span class="bold"><strong>>></strong></span> test whether one node |
| precedes or follows another in document order. Consider this XML |
| document:</p><pre class="programlisting"><book> |
| <title>Being a Dog Is a Full-Time Job</title> |
| <author>Charles M. Schulz</author> |
| <character> |
| <name>Snoopy</name> |
| <friend-of>Peppermint Patty</friend-of> |
| <since>1950-10-04</since> |
| <age>2</age> |
| <qualification>extroverted beagle</qualification> |
| </character> |
| <character> |
| <name>Peppermint Patty</name> |
| <since>1966-08-22>/since> |
| <age>4</age> |
| <qualification>bold, brash and tomboyish</qualification> |
| </character> |
| </book> |
| </pre><p>Example:</p><p><pre class="programlisting">book/character name="Snoopy" << book/character Patty" </pre></p><p><span class="bold"><strong>result:</strong></span></p><div class="orderedlist"><ol type="1"><li><p>xs:boolean: true</p></li></ol></div><p>book/character <a class="ulink" href="name=%22Peppermint" target="_top">Patty"</a> |
| << book/character <a class="ulink" href="name=%22Snoopy%22" target="_top">name="Snoopy"</a> <span class="bold"><strong>result:</strong></span></p><div class="orderedlist"><ol type="1"><li><p>xs:boolean: false</p></li></ol></div></div></body></html> |
