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      xmlns:xlink="http://www.w3.org/1999/xlink"
      xmlns:xi="http://www.w3.org/2001/XInclude"
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      xml:id="ch-expression-language">

<title>Nix Expression Language</title>

<para>The Nix expression language is a pure, lazy, functional
language.  Purity means that operations in the language don't have
side-effects (for instance, there is no variable assignment).
Laziness means that arguments to functions are evaluated only when
they are needed.  Functional means that functions are
<quote>normal</quote> values that can be passed around and manipulated
in interesting ways.  The language is not a full-featured, general
purpose language.  Its main job is to describe packages,
compositions of packages, and the variability within
packages.</para>

<para>This section presents the various features of the
language.</para>

<xi:include href="language-values.xml" />
<xi:include href="language-constructs.xml" />
<xi:include href="language-operators.xml" />
<xi:include href="derivations.xml" />
<xi:include href="builtins.xml" />


</chapter>