File: ACL2-PC_colon__colon_CONTRAPOSE.html

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<head><title>ACL2-PC_colon__colon_CONTRAPOSE.html  --  ACL2 Version 3.1</title></head>
<body text=#000000 bgcolor="#FFFFFF">
<h3>ACL2-PC::CONTRAPOSE</h3>(primitive)
<code>   </code>switch a hypothesis with the conclusion, negating both
<pre>Major Section:  <a href="PROOF-CHECKER-COMMANDS.html">PROOF-CHECKER-COMMANDS</a>
</pre><p>


<pre>
Example:
(contrapose 3)
<p>
General Form:
(contrapose &amp;optional n)
</pre>

The (optional) argument <code>n</code> should be a positive integer that does
not exceed the number of hypotheses.  Negate the current conclusion
and make it the <code>n</code>th hypothesis, while negating the current <code>n</code>th
hypothesis and making it the current conclusion.  If no argument is
supplied then the effect is the same as for <code>(contrapose 1)</code>.<p>

<strong>Note:</strong>  By ``negate'' we mean an operation that replaces <code>nil</code> by <code>t</code>, <code>x</code>
by <code>nil</code> for any other explicit value <code>x</code>, <code>(not x)</code> by <code>x</code>, and any other <code>x</code>
by <code>(not x)</code>.
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