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Diffstat (limited to 'doc/manual/expressions/language-operators.xml')
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diff --git a/doc/manual/expressions/language-operators.xml b/doc/manual/expressions/language-operators.xml new file mode 100644 index 000000000000..a3323ced4c50 --- /dev/null +++ b/doc/manual/expressions/language-operators.xml @@ -0,0 +1,113 @@ +<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> \ No newline at end of file |