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<head><title>SET-WELL-FOUNDED-RELATION.html -- ACL2 Version 3.1</title></head>
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<h2>SET-WELL-FOUNDED-RELATION</h2>set the default well-founded relation
<pre>Major Section: <a href="EVENTS.html">EVENTS</a>
</pre><p>
<pre>
Examples:
(set-well-founded-relation lex2)
</pre>
provided <code>lex2</code> has been proved to be a well-founded relation
(see <a href="WELL-FOUNDED-RELATION.html">well-founded-relation</a>). Note: This is an event! It does
not print the usual event summary but nevertheless changes the ACL2
logical <a href="WORLD.html">world</a> and is so recorded.
<p>
<pre>
General Form:
(set-well-founded-relation rel)
</pre>
where <code>rel</code> has been proved to be a well-founded relation on objects
satisfying some predicate, <code>mp</code>; see <a href="WELL-FOUNDED-RELATION.html">well-founded-relation</a>. This macro is
equivalent to <code>(table acl2-defaults-table :well-founded-relation 'rel)</code>,
and hence is <code><a href="LOCAL.html">local</a></code> to any <a href="BOOKS.html">books</a> and <code><a href="ENCAPSULATE.html">encapsulate</a></code> <a href="EVENTS.html">events</a>
in which it occurs; see <a href="ACL2-DEFAULTS-TABLE.html">acl2-defaults-table</a>.<p>
This event sets the default well-founded relation to be that imposed
on <code>mp</code>-measures by the relation <code>rel</code>. Subsequently, if a recursively
defined function is submitted to <code><a href="DEFUN.html">defun</a></code> with no explicitly given
<code>:</code><code><a href="WELL-FOUNDED-RELATION.html">well-founded-relation</a></code> argument, <code><a href="DEFUN.html">defun</a></code> uses the default relation,
<code>rel</code>, and the associated domain predicate <code>mp</code> used in its
well-foundedness theorem. That is, the termination conditions
generated will require proving that the measure used by the <code><a href="DEFUN.html">defun</a></code> is
an <code>mp</code>-measure and that in every recursive call the measure of the
arguments decreases according to <code>rel</code>.
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