* Strings.
This commit is contained in:
parent
407c9fd520
commit
59ef0aaf3f
1 changed files with 59 additions and 4 deletions
|
@ -595,9 +595,54 @@ language.</para>
|
||||||
|
|
||||||
<itemizedlist>
|
<itemizedlist>
|
||||||
|
|
||||||
<listitem><para><emphasis>Strings</emphasis>,
|
<listitem>
|
||||||
enclosed between double quotes, e.g., <literal>"foo bar"</literal>.
|
|
||||||
TODO: antiquotations, escaping.</para></listitem>
|
<para><emphasis>Strings</emphasis> are enclosed between double
|
||||||
|
quotes, e.g., <literal>"foo bar"</literal>. Strings can span
|
||||||
|
multiple lines. The special characters <literal>"</literal> and
|
||||||
|
<literal>\</literal> and the character sequence
|
||||||
|
<literal>${</literal> must be escaped by prefixing them with a
|
||||||
|
backslash (<literal>\</literal>). Newlines, carriage returns and
|
||||||
|
tabs can be written as <literal>\n</literal>,
|
||||||
|
<literal>\r</literal> and <literal>\t</literal>,
|
||||||
|
respectively.</para>
|
||||||
|
|
||||||
|
<para>You can include the result of an expression into a string by
|
||||||
|
enclosing it in
|
||||||
|
<literal>${<replaceable>...</replaceable>}</literal>, a feature
|
||||||
|
known as <emphasis>antiquotation</emphasis>. The enclosed
|
||||||
|
expression must evaluate to something that can be coerced into a
|
||||||
|
string (meaning that it must be a string, a path, or a
|
||||||
|
derivation). For instance, rather than writing
|
||||||
|
|
||||||
|
<programlisting>
|
||||||
|
"--with-freetype2-library=" + freetype + "/lib"</programlisting>
|
||||||
|
|
||||||
|
(where <varname>freetype</varname> is a derivation), you can
|
||||||
|
instead write the more natural
|
||||||
|
|
||||||
|
<programlisting>
|
||||||
|
"--with-freetype2-library=${freetype}/lib"</programlisting>
|
||||||
|
|
||||||
|
The latter is automatically translated to the former. A more
|
||||||
|
complicated example (from the Nix expression for <link
|
||||||
|
xlink:href='http://www.trolltech.com/products/qt'>Qt</link>):
|
||||||
|
|
||||||
|
<programlisting>
|
||||||
|
configureFlags = "
|
||||||
|
-system-zlib -system-libpng -system-libjpeg
|
||||||
|
${if openglSupport then "-dlopen-opengl
|
||||||
|
-L${mesa}/lib -I${mesa}/include
|
||||||
|
-L${libXmu}/lib -I${libXmu}/include" else ""}
|
||||||
|
${if threadSupport then "-thread" else "-no-thread"}</programlisting>
|
||||||
|
|
||||||
|
Note that Nix expressions and strings can be arbitrarily nested;
|
||||||
|
in this case the outer string contains various antiquotations that
|
||||||
|
themselves contain strings (e.g., <literal>"-thread"</literal>),
|
||||||
|
some of which in turn contain expressions (e.g.,
|
||||||
|
<literal>${mesa}</literal>).</para>
|
||||||
|
|
||||||
|
</listitem>
|
||||||
|
|
||||||
<listitem><para><emphasis>Integers</emphasis>, e.g.,
|
<listitem><para><emphasis>Integers</emphasis>, e.g.,
|
||||||
<literal>123</literal>.</para></listitem>
|
<literal>123</literal>.</para></listitem>
|
||||||
|
@ -1272,7 +1317,17 @@ command-line argument. See <xref linkend='sec-standard-environment'
|
||||||
|
|
||||||
<section><title>Built-in functions</title>
|
<section><title>Built-in functions</title>
|
||||||
|
|
||||||
<para>TODO</para>
|
<para>This section lists the functions and constants built into the
|
||||||
|
Nix expression evaluator. (The built-in function
|
||||||
|
<function>derivation</function> is discussed above.) Some built-ins,
|
||||||
|
such as <function>derivation</function>, are always in scope of every
|
||||||
|
Nix expression; you can just access them right away. But to prevent
|
||||||
|
polluting the namespace too much, most built-ins are not in scope.
|
||||||
|
Instead, you can access them through the <varname>builtins</varname>
|
||||||
|
built-in value, which is an attribute set that contains all built-in
|
||||||
|
functions and values. For instance, <function>derivation</function>
|
||||||
|
is also available as <function>builtins.derivation</function>.</para>
|
||||||
|
|
||||||
|
|
||||||
<variablelist>
|
<variablelist>
|
||||||
|
|
||||||
|
|
Loading…
Reference in a new issue