next | previous | forward | backward | up | index | toc

# boundaryCells -- returns the boundary cells of the given cell

## Synopsis

• Usage:
boundaryCells(C)
• Inputs:
• C, a cell, whose boundary is to be returned
• Outputs:
• a list, of the cells in the boundary of C

## Description

Given a cell C, this command returns a list whose elements are the boundary cells of C. This differs from boundary in that it returns only the boundary cells of C, whereas boundaryCells returns a list of two-element sequences of the boundary cells and their corresponding orientation.

 i1 : R = QQ[x,y,z]; i2 : vx = newSimplexCell({},x); i3 : vy = newSimplexCell({},y); i4 : vz = newSimplexCell({},z); i5 : exy = newSimplexCell {vx,vy}; i6 : C = cellComplex(R,{exy,vz}); i7 : boundaryCells(exy) o7 = {Cell of dimension 0 with label x, Cell of dimension 0 with label y} o7 : List i8 : boundaryCells(vz) o8 = {} o8 : List
 i9 : R = QQ; i10 : P = convexHull matrix {{1,1,-1,-1},{1,-1,1,-1}}; i11 : C = cellComplex(R,P); i12 : f = (cells(2,C))#0; i13 : boundaryCells(f) o13 = {Cell of dimension 1 with label 1, Cell of dimension 1 with label 1, ----------------------------------------------------------------------- Cell of dimension 1 with label 1, Cell of dimension 1 with label 1} o13 : List