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   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>obtain</title><link rel="stylesheet" type="text/css" href="docbook.css" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="home" href="index.html" title="Matita V0.99.5 User Manual (rev. 0.99.5 )" /><link rel="up" href="sec_declarative_tactics.html" title="Chapter 8. Declarative Tactics" /><link rel="prev" href="tac_conclude.html" title="conclude" /><link rel="next" href="tac_rewrite_step.html" title="=" /></head><body><a xmlns="" href="../../../"><div class="matita_logo"><img src="figures/matita.png" alt="Tiny Matita logo" /><span>Matita Home</span></div></a><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">obtain</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="tac_conclude.html">Prev</a> </td><th width="60%" align="center">Chapter 8. Declarative Tactics</th><td width="20%" align="right"> <a accesskey="n" href="tac_rewrite_step.html">Next</a></td></tr></table><hr /></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="tac_obtain"></a>obtain</h2></div></div></div><p><strong class="userinput"><code>obtain H t1 </code></strong></p><p>
   3       </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Synopsis:</span></dt><dd><p><span class="bold"><strong>obtain</strong></span> <span class="emphasis"><em><a class="link" href="sec_terms.html#grammar.id">id</a></em></span> <span class="emphasis"><em><a class="link" href="sec_terms.html#grammar.term">term</a></em></span></p></dd><dt><span class="term">Pre-condition:</span></dt><dd><p>
   4                  None.
   5              </p></dd><dt><span class="term">Action:</span></dt><dd><p>It starts an equality chain <span class="command"><strong>t1 = ?</strong></span>, which, when concluded, will be added to hypoteses of the current sequent. It allows the user to apply the tactic <span class="bold"><strong>=</strong></span> to continue the chain.</p></dd><dt><span class="term">New sequent to prove:</span></dt><dd><p>A new sequent for <span class="command"><strong>t1 = ?</strong></span> is opened, a new sequent for <span class="command"><strong>?</strong></span> is opened, and a new sequent with the conclusion of the sequent on which this tactic was applied is opened, with <span class="command"><strong>H: t1 = ?</strong></span> added to its hypotheses. This hypotesis will be changed when the equality chain is concluded with <span class="command"><strong>H: t1 = tk</strong></span>, where <span class="command"><strong>tk</strong></span> is the last term of the equality chain. The goal for <span class="command"><strong>?</strong></span> can be safely ignored, as it will be automatically closed when the equality chain is concluded.</p></dd></dl></div><p>
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