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<div class="add">

<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="glib_000.html#NM2">_Graph</a>;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="glib_000.html#NM10">Vertex</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>



<b>set </b><font color="Maroon">c<sub>3</sub></font> = <font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font>;<br/>
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K3" target="_self">.first()</a>  = 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> 1

<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p2">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="finseq_1.html#T57">FINSEQ_1:57</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K4" target="_self">.last()</a> 

;<br/>
<b>hence </b><a NAME="E2:38"/>
<font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font> is <a href="glib_001.html#V1" target="_self">closed</a>
 <b>by </b><i><a class="ref" href="glib_001.html#D24" target="_self">Def24</a></i>;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="38_2"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">c<sub>4</sub></font> be  <a href="abian.html#V1">odd</a> <a href="nat_1.html#NM1">Nat</a>;<br/><b>assume </b><a NAME="E1:38_2"/>
<font color="Maroon">c<sub>4</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a>  <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span>
 ;<br/><a NAME="E2:38_2"/><b>then </b>
<font color="Maroon">c<sub>4</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a> 1
 <b>by </b><i><a class="ref" href="finseq_1.html#T56">FINSEQ_1:56</a></i>;<br/><b>hence </b><a NAME="E3:38_2"/>
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="glib_000.html#K10">the_Source_of</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="nat_1.html#K1">+</a> 1</span>)</span></span>)</span>
 <b>by </b><i><a class="ref" href="heyting3.html#T1">HEYTING3:1</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E4:38"/>
<font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font> is <a href="glib_001.html#V2" target="_self">directed</a>
 <b>by </b><i><a class="ref" href="glib_001.html#D25" target="_self">Def25</a></i>;<br/>

<a NAME="E5:38"/>
 <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="hidden.html#R1">=</a> 1
 
<b>by </b><i><a class="ref" href="finseq_1.html#T56">FINSEQ_1:56</a></i>;<br/>
<a NAME="E6:38"/><b>then </b>
0 <a href="nat_1.html#K1">+</a> 1 <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default">2 <a href="nat_1.html#K2">*</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p3">(<span class="default"><span class="p4">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span></span>)</span></span>)</span> <a href="nat_1.html#K1">+</a> 1
 
<b>by </b><i><a class="ref" href="glib_001.html#D15" target="_self">Def15</a></i>;<br/>
<a NAME="E7:38"/><b>then </b>
0 <a href="hidden.html#R1">=</a> 2 <a href="nat_1.html#K2">*</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p2">(<span class="default"><span class="p3">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span></span>)</span>
 
;<br/>
<a NAME="E8:38"/><b>then </b>
0 <a href="hidden.html#R1">=</a>  <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span>
 
;<br/>
<a NAME="E9:38"/><b>then </b>
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K15" target="_self">.length()</a>  <a href="hidden.html#R1">=</a> 0
 
;<br/>
<b>hence </b><a NAME="E10:38"/>
<font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font> is <a href="glib_001.html#V3" target="_self">trivial</a>
 <b>by </b><i><a class="ref" href="glib_001.html#D26" target="_self">Def26</a></i>;<br/>

<a NAME="E11:38"/>
 <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default">2 <a href="nat_1.html#K2">*</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p3">(<span class="default"><span class="p4">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span></span>)</span></span>)</span> <a href="nat_1.html#K1">+</a> 1
 
<b>by </b><i><a class="ref" href="glib_001.html#D15" target="_self">Def15</a></i>;<br/>
<a NAME="E12:38"/><b>then </b>
0 <a href="nat_1.html#K1">+</a> 1 <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default">2 <a href="nat_1.html#K2">*</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p3">(<span class="default"><span class="p4">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span></span>)</span></span>)</span> <a href="nat_1.html#K1">+</a> 1
 
<b>by </b><i><a class="ref" href="finseq_1.html#T57">FINSEQ_1:57</a></i>;<br/>
<a NAME="E13:38"/><b>then </b>
0 <a href="hidden.html#R1">=</a> 2 <a href="nat_1.html#K2">*</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p2">(<span class="default"><span class="p3">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span></span>)</span>
 
;<br/>
<a NAME="E14:38"/><b>then </b>
 <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a> </span>)</span> <a href="hidden.html#R1">=</a> 0
 
;<br/>
<a NAME="E15:38"/><b>then </b>
<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="glib_001.html#K12" target="_self">.edgeSeq()</a>  is <a href="funct_1.html#V2">one-to-one</a>
 
<b>by </b><i><a class="ref" href="finseq_1.html#T25">FINSEQ_1:25</a></i>;<br/>
<b>hence </b><a NAME="E16:38"/><i><font color="Green">E36</font></i>: 
<font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font> is <a href="glib_001.html#V4" target="_self">Trail-like</a>
 <b>by </b><i><a class="ref" href="glib_001.html#D27" target="_self">Def27</a></i>;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="38_3"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">c<sub>4</sub></font>, <font color="Maroon">c<sub>5</sub></font> be  <a href="abian.html#V1">odd</a> <a href="nat_1.html#NM1">Nat</a>;<br/><b>assume </b><a NAME="E1:38_3"/>
( <font color="Maroon">c<sub>4</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Maroon">c<sub>5</sub></font> &amp; <font color="Maroon">c<sub>5</sub></font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> )
 ;<br/><a NAME="E2:38_3"/><b>then </b>
( <font color="Maroon">c<sub>4</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Maroon">c<sub>5</sub></font> &amp; <font color="Maroon">c<sub>5</sub></font> <a href="xxreal_0.html#R1">&lt;=</a> 1 )
 <b>by </b><i><a class="ref" href="finseq_1.html#T57">FINSEQ_1:57</a></i>;<br/><a NAME="E3:38_3"/><b>then </b>
<font color="Maroon">c<sub>4</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a> 1
 <b>by </b><i><a class="ref" href="xxreal_0.html#T2">XXREAL_0:2</a></i>;<br/><b>hence </b><a NAME="E4:38_3"/>
( <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">c<sub>5</sub></font> implies ( <font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#R1">=</a> 1 &amp; <font color="Maroon">c<sub>5</sub></font> <a href="hidden.html#R1">=</a>  <a href="finseq_1.html#K3">len</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> ) )
 <b>by </b><i><a class="ref" href="heyting3.html#T1">HEYTING3:1</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E18:38"/>
<font color="Maroon">c<sub>1</sub></font> <a href="glib_001.html#K1" target="_self">.walkOf</a> <font color="Maroon">c<sub>2</sub></font> is <a href="glib_001.html#V5" target="_self">Path-like</a>
 <b>by </b><i><a class="txt" href="glib_001.html#E16:38"><i><font color="Green">E36</font></i></a>, <a class="ref" href="glib_001.html#D28" target="_self">Def28</a></i>;<br/>


</div>
