e. Then the clause is written actually as a list of clauses.

<p>For example, a generator clause to search for a customer by phone number is

<pre>
(tel +CuSu @Tel)
</pre>

If we want to search for a customer without knowing whether a given number is a
normal or a mobile phone number, then a combined generator clause searching both
index trees could look like

<pre>
((tel +CuSu @Tel  mob +CuSu @Tel))
</pre>

<p>The generator will first traverse all matching entries in the <code><a
href="refR.html#+Ref">+Ref