forked from lix-project/lix
113 lines
4 KiB
XML
113 lines
4 KiB
XML
|
<section xmlns="http://docbook.org/ns/docbook"
|
|||
|
|
xmlns:xlink="http://www.w3.org/1999/xlink"
|
|||
|
|
xmlns:xi="http://www.w3.org/2001/XInclude"
|
|||
|
|
version="5.0"
|
|||
|
|
xml:id="sec-language-operators">
|
|||
|
|
|
|||
|
|
<title>Operators</title>
|
|||
|
|
|
|||
|
|
<para><xref linkend='table-operators' /> lists the operators in the
|
|||
|
|
Nix expression language, in order of precedence (from strongest to
|
|||
|
|
weakest binding).</para>
|
|||
|
|
|
|||
|
|
<table xml:id='table-operators'>
|
|||
|
|
<title>Operators</title>
|
|||
|
|
<tgroup cols='3'>
|
|||
|
|
<thead>
|
|||
|
|
<row>
|
|||
|
|
<entry>Syntax</entry>
|
|||
|
|
<entry>Associativity</entry>
|
|||
|
|
<entry>Description</entry>
|
|||
|
|
</row>
|
|||
|
|
</thead>
|
|||
|
|
<tbody>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e</replaceable> <literal>.</literal>
|
|||
|
|
<replaceable>attrpath</replaceable>
|
|||
|
|
[ <literal>or</literal> <replaceable>def</replaceable> ]
|
|||
|
|
</entry>
|
|||
|
|
<entry>none</entry>
|
|||
|
|
<entry>Select attribute denoted by the attribute path
|
|||
|
|
<replaceable>attrpath</replaceable> from set
|
|||
|
|
<replaceable>e</replaceable>. (An attribute path is a
|
|||
|
|
dot-separated list of attribute names.) If the attribute
|
|||
|
|
doesn’t exist, return <replaceable>def</replaceable> if
|
|||
|
|
provided, otherwise abort evaluation.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>left</entry>
|
|||
|
|
<entry>Call function <replaceable>e1</replaceable> with
|
|||
|
|
argument <replaceable>e2</replaceable>.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e</replaceable> <literal>?</literal>
|
|||
|
|
<replaceable>attrpath</replaceable></entry>
|
|||
|
|
<entry>none</entry>
|
|||
|
|
<entry>Test whether set <replaceable>e</replaceable> contains
|
|||
|
|
the attribute denoted by <replaceable>attrpath</replaceable>;
|
|||
|
|
return <literal>true</literal> or
|
|||
|
|
<literal>false</literal>.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>++</literal> <replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>right</entry>
|
|||
|
|
<entry>List concatenation.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>+</literal> <replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>left</entry>
|
|||
|
|
<entry>String or path concatenation.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><literal>!</literal> <replaceable>e</replaceable></entry>
|
|||
|
|
<entry>left</entry>
|
|||
|
|
<entry>Boolean negation.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>//</literal>
|
|||
|
|
<replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>right</entry>
|
|||
|
|
<entry>Return a set consisting of the attributes in
|
|||
|
|
<replaceable>e1</replaceable> and
|
|||
|
|
<replaceable>e2</replaceable> (with the latter taking
|
|||
|
|
precedence over the former in case of equally named
|
|||
|
|
attributes).</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>==</literal>
|
|||
|
|
<replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>none</entry>
|
|||
|
|
<entry>Equality.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>!=</literal>
|
|||
|
|
<replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>none</entry>
|
|||
|
|
<entry>Inequality.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>&&</literal>
|
|||
|
|
<replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>left</entry>
|
|||
|
|
<entry>Logical AND.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>||</literal>
|
|||
|
|
<replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>left</entry>
|
|||
|
|
<entry>Logical OR.</entry>
|
|||
|
|
</row>
|
|||
|
|
<row>
|
|||
|
|
<entry><replaceable>e1</replaceable> <literal>-></literal>
|
|||
|
|
<replaceable>e2</replaceable></entry>
|
|||
|
|
<entry>none</entry>
|
|||
|
|
<entry>Logical implication (equivalent to
|
|||
|
|
<literal>!<replaceable>e1</replaceable> ||
|
|||
|
|
<replaceable>e2</replaceable></literal>).</entry>
|
|||
|
|
</row>
|
|||
|
|
</tbody>
|
|||
|
|
</tgroup>
|
|||
|
|
</table>
|
|||
|
|
|
|||
|
|
</section>
|