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<head><title>ER-PROGN.html -- ACL2 Version 3.1</title></head>
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<h2>ER-PROGN</h2>perform a sequence of state-changing ``error triples''
<pre>Major Section: <a href="PROGRAMMING.html">PROGRAMMING</a>
</pre><p>
<pre>
Example:
(er-progn (check-good-foo-p (f-get-global 'my-foo state) state)
(value (* (f-get-global 'my-foo state)
(f-get-global 'bar state))))
</pre>
<p>
This sequencing primitive is only useful when programming with
<a href="STATE.html">state</a>, something that very few users will probably want to do.
See <a href="STATE.html">state</a>.
<p>
<code>Er-progn</code> is used much the way that <code><a href="PROGN.html">progn</a></code> is used in Common
Lisp, except that it expects each form within it to evaluate to an
``error triple'' of the form <code>(mv erp val state)</code>. The first such
form, if any, that evaluates to such a triple where <code>erp</code> is not
<code>nil</code> yields the error triple returned by the <code>er-progn</code>. If
there is no such form, then the last form returns the value of the
<code>er-progn</code> form.<p>
We intend to write more about this topic, especially if there are
requests to do so.
<br><br><br><a href="acl2-doc.html"><img src="llogo.gif"></a> <a href="acl2-doc-index.html"><img src="index.gif"></a>
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