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<head><title>ACL2-PC_colon__colon_DV.html -- ACL2 Version 3.1</title></head>
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<h3>ACL2-PC::DV</h3>(atomic macro)
<code> </code>move to the indicated subterm
<pre>Major Section: <a href="PROOF-CHECKER-COMMANDS.html">PROOF-CHECKER-COMMANDS</a>
</pre><p>
<pre>
Examples:
(dv 1) -- assign the new current subterm to be the first argument
of the existing current subterm
(dv 1 2) -- assign the new current subterm to be the result of
first taking the 1st argument of the existing
current subterm, and then the 2nd argument of that
</pre>
For example, if the current subterm is
<pre>
(* (+ a b) c),
</pre>
then after <code>(dv 1)</code> it is
<pre>
(+ a b).
</pre>
If after that, then <code>(dv 2)</code> is invoked, the new current subterm
will be
<pre>
b.
</pre>
Instead of <code>(dv 1)</code> followed by <code>(dv 2)</code>, the same current subterm
could be obtained by instead submitting the single instruction
<code>(dv 1 2)</code>.
<p>
<pre>
General Form:
(dv &rest naturals-list)
</pre>
If <code>naturals-list</code> is a non-empty list <code>(n_1 ... n_k)</code> of natural
numbers, let the new current subterm be the result of selecting the
<code>n_1</code>-st argument of the current subterm, and then the <code>n_2</code>-th subterm
of that, ..., finally the <code>n_k</code>-th subterm.<p>
<strong>Note:</strong> <code>(dv n)</code> may be abbreviated by simply <code>n</code>, so we could have typed
<code>1</code> instead of <code>(dv 1)</code> in the first example above.<p>
<strong>Note:</strong> See also <code>dive</code>, which is related to the command <code>pp</code>, in that
the diving is done according to raw (translated, internal form)
syntax. Use the command <code>dv</code> if you want to dive according to the
syntax displayed by the command <code>p</code>.
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