<Verb>PiZero(Y):: RegCWComplex --> List</Verb>
<Verb>PiZero(Y):: Graph --> List</Verb>
<Verb>PiZero(Y):: SimplicialComplex --> List</Verb><P/>

<P/> Inputs a regular CW-complex <M>Y</M>, or graph <M>Y</M>, or simplicial complex <M>Y</M> 
and returns a pair <M>[cells,r]</M> where: <M>cells</M> is a list of
vertices of $Y$ representing the distinct path-components; <M>r(v)</M>
is a function which, for each vertex <M>v</M> of <M>Y</M> returns the representative vertex <M>r(v) \in cells</M>. 


