### 38 Some functions for accessing basic data

#### 38.1

##### 38.1-1 BoundaryMap
 ‣ BoundaryMap( C ) ( function )

Inputs a resolution, chain complex or cochain complex C and returns the function C!.boundary.

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##### 38.1-2 BoundaryMatrix
 ‣ BoundaryMatrix( C, n ) ( function )

Inputs a chain or cochain complex C and integer n>0. It returns the n-th boundary map of C as a matrix.

##### 38.1-3 Dimension
 ‣ Dimension( C ) ( function )
 ‣ Dimension( M ) ( function )

Inputs a resolution, chain complex or cochain complex C and returns the function C!.dimension .

Alternatively, inputs an FpG-module M and returns its dimension as a vector space over the field of p elements.

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##### 38.1-4 EvaluateProperty
 ‣ EvaluateProperty( X, str ) ( function )

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

##### 38.1-5 GroupOfResolution
 ‣ GroupOfResolution( R ) ( function )

Inputs a ZG-resolution R and returns the group G.

##### 38.1-6 Length
 ‣ Length( R ) ( function )

Inputs a resolution R and returns its length (i.e. the number of terms of R that HAP has computed).

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##### 38.1-7 Map
 ‣ Map( f ) ( function )

Inputs a chain map, or cochain map or equivariant chain map f and returns the mapping function (as opposed to the target or the source of f) .

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##### 38.1-8 Source
 ‣ Source( f ) ( function )

Inputs a chain map, or cochain map, or equivariant chain map, or FpG-module homomorphism f and returns it source.

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##### 38.1-9 Target
 ‣ Target( f ) ( function )

Inputs a chain map, or cochain map, or equivariant chain map, or FpG-module homomorphism f and returns its target.

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