<Chapter><Heading> Some functions for accessing basic data</Heading>

<Table Align="|l|" >

<Row>
<Item>
<Index> BoundaryMap</Index>
<C>
BoundaryMap(C)
</C>
<P/>

Inputs a resolution, chain complex or cochain complex <M>C</M>
and returns the function <M>C!.boundary</M>.
</Item>
</Row>
<Row>
<Item>
<Index> BoundaryMatrix</Index>
<C>
BoundaryMatrix(C,n)
</C>
<P/>

Inputs a chain or cochain complex <M>C</M> and integer <M>n</M>&tgt;<M>0</M>. It returns the <M>n</M>-th boundary map of <M>C</M> as a matrix.
</Item>
</Row>
<Row>
<Item>
<Index> Dimension</Index> 
<C>
Dimension(C)
</C>
<Br/>
<C>
Dimension(M)
</C>
<P/>

Inputs a resolution, chain complex or cochain complex <M>C</M>
and returns the function <M>C!.dimension</M> .
<P/>
Alternatively, inputs an <M>FpG</M>-module <M>M</M>
and returns its dimension as a vector space over the field of <M>p</M>
elements.
</Item>
</Row>
<Row>
<Item>
<Index> EvaluateProperty</Index>
<C>
EvaluateProperty(X,"name")
</C>
<P/>

Inputs a component object <M>X</M> 
(such as a <M>ZG</M>-resolution or chain map) and a string 
"name" (such as "characteristic" or "type"). It searches <M>X.property</M> for the  pair ["name",value] and returns value. If <M>X.property</M>
does not exist, or if ["name",value] does not exist, it returns fail.
</Item>
</Row>

<Row>
<Item>
<Index> GroupOfResolution</Index>
<C>
GroupOfResolution(R)
</C>
<P/>

Inputs a <M>ZG</M>-resolution <M>R</M> and returns the group <M>G</M>.
</Item>
</Row>
<Row>
<Item>
<Index> Length</Index>
<C>
Length(R)
</C>
<P/>

Inputs a resolution <M>R</M> and returns its length 
(i.e. the number of terms of <M>R</M> that HAP has computed). 
</Item>
</Row>
<Row>
<Item>
<Index> Map</Index>
<C>
Map(f)
</C>
<P/>

Inputs a chain map, or cochain map or equivariant chain map <M>f</M>
and returns the mapping function (as opposed to the 
target or the source of <M>f</M>) .
</Item>
</Row>

<Row>
<Item>
<Index> Source</Index>
<C>
Source(f)
</C>
<P/>

Inputs a chain map, or cochain map, or equivariant chain map, or 
<M>FpG</M>-module homomorphism <M>f</M> and returns it source.
</Item>
</Row>

<Row>
<Item>
<Index> Target</Index>
<C>
Target(f)
</C>
<P/>

Inputs a chain map, or cochain map, or equivariant chain map, or 
<M>FpG</M>-module homomorphism <M>f</M> and returns its target.
</Item>
</Row>




</Table>
</Chapter>