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<b>let </b><font color="Maroon">x</font> be   <a href="zf_lang.html#NM1">Variable</a>;<br/><b>let </b><font color="Maroon">y</font> be   <a href="zf_lang.html#NM1">Variable</a>;<br/>



<a NAME="E1:2"/>
<font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">y</font> <a href="zf_lang.html#NR2" target="_self">is_membership</a> 
 
<b>by </b><i><a class="ref" href="zf_lang.html#T16">ZF_LANG:16</a></i>;<br/>
<a NAME="E2:2"/><b>then </b>
<font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">y</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K18">Var1</a> <span class="p2">(<span class="default"><font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">y</font></span>)</span></span>)</span> <a href="zf_lang.html#K5">'in'</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K19">Var2</a> <span class="p2">(<span class="default"><font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">y</font></span>)</span></span>)</span>
 
<b>by </b><i><a class="ref" href="zf_lang.html#T54">ZF_LANG:54</a></i>;<br/>
<b>hence </b><a NAME="E3:2"/>
(  <a href="zf_lang.html#K18">Var1</a> <span class="p1">(<span class="default"><font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">y</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font> &amp;  <a href="zf_lang.html#K19">Var2</a> <span class="p1">(<span class="default"><font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">y</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">y</font> )
 <b>by </b><i><a class="ref" href="zf_lang.html#T7">ZF_LANG:7</a></i>;<br/>


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