DOLFIN User Manual - FEniCS Project

DOLFIN User ManualHoffman, Jansson, Logg, WellsThe following example illustrates how to create such as Function by overloadingthe eval() function:class MeshSize : public Function{real eval(const Point& p, unsigned int i){return cell().diameter();}}MeshSize h;Note that the current Cell is only available during assembly and has nomeaning otherwise. It is thus not possible to write the Function h to file,since the current Cell is not available when evaluating a Function at anygiven Vertex. Furthermore, note that the current Cell is not available whencreating a Function from a function pointer.5.4 Time-dependent functions◮ Developer’s note: Write about time-dependent and pseudo time-dependentfunctions.42