* Operators, comments.
This commit is contained in:
Eelco Dolstra
parent
55b35d6d77
commit
1bac7a10e6
|
|
@ -933,14 +933,126 @@ used in the Nix expression for Subversion.</para>
|
|||
|
||||
<simplesect><title>With expressions</title>
|
||||
|
||||
<para>TODO</para>
|
||||
<para>A <emphasis>with</emphasis> expression,
|
||||
|
||||
<programlisting>
|
||||
with <replaceable>e1</replaceable>; <replaceable>e2</replaceable></programlisting>
|
||||
|
||||
introduces the attribute set <replaceable>e1</replaceable> into the
|
||||
lexical scope of the expression <replaceable>e2</replaceable>. For
|
||||
instance,
|
||||
|
||||
<programlisting>
|
||||
let {
|
||||
as = {x = "foo"; y = "bar";};
|
||||
|
||||
body = with as; x + y;
|
||||
}</programlisting>
|
||||
|
||||
evaluates to <literal>"foobar"</literal> since the
|
||||
<literal>with</literal> adds the <varname>x</varname> and
|
||||
<varname>y</varname> attributes of <varname>as</varname> to the
|
||||
lexical scope in the expression <literal>x + y</literal>. The most
|
||||
common use of <literal>with</literal> is in conjunction with the
|
||||
<function>import</function> function. E.g.,
|
||||
|
||||
<programlisting>
|
||||
with (import ./definitions.nix); ...</programlisting>
|
||||
|
||||
makes all attributes defined in the file
|
||||
<filename>definitions.nix</filename> available as if they were defined
|
||||
locally in a <literal>rec</literal>-expression.</para>
|
||||
|
||||
</simplesect>
|
||||
|
||||
|
||||
<simplesect><title>Operators</title>
|
||||
|
||||
<para>TODO</para>
|
||||
<para><xref linkend='table-operators' /> lists the operators in the
|
||||
Nix expression language, in order of precedence (from strongest to
|
||||
weakest binding).</para>
|
||||
|
||||
<table 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>e1</replaceable> ~ <replaceable>e2</replaceable></entry>
|
||||
<entry>none</entry>
|
||||
<entry>Construct a reference to a subpath of a derivation.
|
||||
E.g., <literal>hello ~ "/bin/sh"</literal> refers to the
|
||||
<filename>/bin/sh</filename> path within the Hello derivation.
|
||||
Useful in specifying derivation attributes.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e</replaceable> ?
|
||||
<replaceable>id</replaceable></entry>
|
||||
<entry>none</entry>
|
||||
<entry>Test whether attribute set <replaceable>e</replaceable>
|
||||
contains an attribute named
|
||||
<replaceable>id</replaceable>.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e1</replaceable> + <replaceable>e2</replaceable></entry>
|
||||
<entry>left</entry>
|
||||
<entry>String or path concatenation.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry>! <replaceable>e</replaceable></entry>
|
||||
<entry>left</entry>
|
||||
<entry>Boolean negation.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e1</replaceable> //
|
||||
<replaceable>e2</replaceable></entry>
|
||||
<entry>right</entry>
|
||||
<entry>Return an attribute 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> ==
|
||||
<replaceable>e2</replaceable></entry>
|
||||
<entry>none</entry>
|
||||
<entry>Equality.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e1</replaceable> !=
|
||||
<replaceable>e2</replaceable></entry>
|
||||
<entry>none</entry>
|
||||
<entry>Inequality.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e1</replaceable> &&
|
||||
<replaceable>e2</replaceable></entry>
|
||||
<entry>left</entry>
|
||||
<entry>Logical AND.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e1</replaceable> ||
|
||||
<replaceable>e2</replaceable></entry>
|
||||
<entry>left</entry>
|
||||
<entry>Logical OR.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><replaceable>e1</replaceable> ->
|
||||
<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>
|
||||
|
||||
</simplesect>
|
||||
|
||||
|
|
@ -959,6 +1071,15 @@ used in the Nix expression for Subversion.</para>
|
|||
</simplesect>
|
||||
|
||||
|
||||
<simplesect><title>Comments</title>
|
||||
|
||||
<para>Comments can be single-line, started with a <literal>#</literal>
|
||||
character, or inline/multi-line, enclosed within <literal>/*
|
||||
... */</literal>.</para>
|
||||
|
||||
</simplesect>
|
||||
|
||||
|
||||
</sect1>
|
||||
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue