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Document some primops

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This commit is contained in:
Eelco Dolstra 2014-10-29 16:18:03 +01:00
parent 11aef17a77
commit 722bd041ce
1 changed files with 52 additions and 12 deletions
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64
doc/manual/expressions/builtins.xml
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@ -45,14 +45,17 @@ available as <function>builtins.derivation</function>.</para>
<listitem><para>Return the names of the attributes in the set
<replaceable>set</replaceable> in a sorted list. For instance,
<literal>builtins.attrNames { y = 1; x = "foo"; }</literal>
evaluates to <literal>[ "x" "y" ]</literal>. There is no built-in
function <function>attrValues</function>, but you can easily
define it yourself:
evaluates to <literal>[ "x" "y" ]</literal>.</para></listitem>
<programlisting>
attrValues = set: map (name: builtins.getAttr name set) (builtins.attrNames set);</programlisting>
</varlistentry>
</para></listitem>
<varlistentry><term><function>builtins.attrValues</function>
<replaceable>set</replaceable></term>
<listitem><para>Return the values of the attributes in the set
<replaceable>set</replaceable> in the order corresponding to the
sorted attribute names.</para></listitem>
</varlistentry>
@ -144,6 +147,19 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
-->
<varlistentry><term><function>builtins.deepSeq</function>
<replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
<listitem><para>This is like <literal>seq
<replaceable>e1</replaceable>
<replaceable>e2</replaceable></literal>, except that
<replaceable>e1</replaceable> is evaluated
<emphasis>deeply</emphasis>: if it’s a list or set, its elements
or attributes are also evaluated recursively.</para></listitem>
</varlistentry>
<varlistentry><term><function>derivation</function>
<replaceable>attrs</replaceable></term>
@ -596,13 +612,26 @@ in config.someSetting</programlisting>
</varlistentry>
<!--
<varlistentry><term><function>relativise</function></term>
<varlistentry><term><function>builtins.readDir</function>
<replaceable>path</replaceable></term>
<listitem><para>TODO</para></listitem>
<listitem><para>Return the contents of the directory
<replaceable>path</replaceable> as a set mapping directory entries
to the corresponding file type. For instance, if directory
<filename>A</filename> contains a regular file
<filename>B</filename> and another directory
<filename>C</filename>, then <literal>builtins.readDir
./A</literal> will return the set
<programlisting>
{ A = "regular"; B = "directory"; }</programlisting>
The possible values for the file type are
<literal>"regular"</literal>, <literal>"directory"</literal>,
<literal>"symlink"</literal> and
<literal>"unknown"</literal>.</para></listitem>
</varlistentry>
-->
<varlistentry><term><function>builtins.readFile</function>
@ -622,14 +651,25 @@ in config.someSetting</programlisting>
<replaceable>set</replaceable>. The attributes don’t have to
exist in <replaceable>set</replaceable>. For instance,
<screen>
removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>
<programlisting>
removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</programlisting>
evaluates to <literal>{ y = 2; }</literal>.</para></listitem>
</varlistentry>
<varlistentry><term><function>builtins.seq</function>
<replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
<listitem><para>Evaluate <replaceable>e1</replaceable>, then
evaluate and return <replaceable>e2</replaceable>. This ensures
that a computation is strict in the value of
<replaceable>e1</replaceable>.</para></listitem>
</varlistentry>
<varlistentry><term><function>builtins.stringLength</function>
<replaceable>e</replaceable></term>