<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>