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<b>let </b><font color="Maroon" title="c1">G</font> be  non <a href="struct_0.html#V3" title="STRUCT_0:attr.3">empty</a>  <a href="lang1.html#L2" title="LANG1:struct.2">GrammarStr</a> ;<br/><b>let </b><font color="Maroon" title="c2">n</font> be   <a href="lang1.html#NM2" title="LANG1:NM.2">String</a> of <font color="Maroon" title="c1">G</font>;<br/>



<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="23_1"><b>now </b></a><div class="add"><b>assume </b><a NAME="E1:23_1"/>
<font color="Maroon" title="c2">n</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="lang1.html#K7" title="LANG1:func.7">Lang</a> <font color="Maroon" title="c1">G</font>
 ;<br/><a NAME="E2:23_1"/><b>then </b>
 ex <font color="Olive" title="b1">a</font> being   <a href="finseq_2.html#M2" title="FINSEQ_2:mode.2">Element</a> of the <a href="struct_0.html#U1" title="STRUCT_0:sel.1">carrier</a> of <font color="Maroon" title="c1">G</font> <a href="finseq_2.html#K3" title="FINSEQ_2:func.3">*</a>  st <br/>( <font color="Maroon" title="c2">n</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Olive" title="b1">a</font> &amp;  <a href="relset_1.html#K5" title="RELSET_1:func.5">rng</a> <font color="Olive" title="b1">a</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="lang1.html#K5" title="LANG1:func.5">Terminals</a> <font color="Maroon" title="c1">G</font> &amp; <font color="Olive" title="b1">a</font> <a href="lang1.html#R3" title="LANG1:pred.3">is_derivable_from</a> <span class="p1"><a href="lang1.html#K3" title="LANG1:func.3">&lt;*</a><span class="default">the <a href="lang1.html#U2" title="LANG1:sel.2">InitialSym</a> of <font color="Maroon" title="c1">G</font></span><a href="lang1.html#K3" title="LANG1:func.3">*&gt;</a></span> )
 ;<br/><b>hence </b><a NAME="E3:23_1"/>
(  <a href="relset_1.html#K5" title="RELSET_1:func.5">rng</a> <font color="Maroon" title="c2">n</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="lang1.html#K5" title="LANG1:func.5">Terminals</a> <font color="Maroon" title="c1">G</font> &amp; <font color="Maroon" title="c2">n</font> <a href="lang1.html#R3" title="LANG1:pred.3">is_derivable_from</a> <span class="p1"><a href="lang1.html#K3" title="LANG1:func.3">&lt;*</a><span class="default">the <a href="lang1.html#U2" title="LANG1:sel.2">InitialSym</a> of <font color="Maroon" title="c1">G</font></span><a href="lang1.html#K3" title="LANG1:func.3">*&gt;</a></span> )
 ;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E2:23"/>
( <font color="Maroon" title="c2">n</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="lang1.html#K7" title="LANG1:func.7">Lang</a> <font color="Maroon" title="c1">G</font> iff (  <a href="relset_1.html#K5" title="RELSET_1:func.5">rng</a> <font color="Maroon" title="c2">n</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="lang1.html#K5" title="LANG1:func.5">Terminals</a> <font color="Maroon" title="c1">G</font> &amp; <font color="Maroon" title="c2">n</font> <a href="lang1.html#R3" title="LANG1:pred.3">is_derivable_from</a> <span class="p1"><a href="lang1.html#K3" title="LANG1:func.3">&lt;*</a><span class="default">the <a href="lang1.html#U2" title="LANG1:sel.2">InitialSym</a> of <font color="Maroon" title="c1">G</font></span><a href="lang1.html#K3" title="LANG1:func.3">*&gt;</a></span> ) )
 ;<br/>


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