Templating

Yggdrasil uses templated classes predominantly to allow the user to specify the number of dimensions in a class without having to write out the same code multiple times. Most classes that are going to interact with other templated classes from within Yggdrasil should follow the convention of using template <int dim>.

For instance, template <int dim> class RungeKutta2Integrator : public Integrator<dim> is a templated RK2 integrator class that inherits from the base integrator templated class. This way, other classes used throughout the derived class will have the proper dimensionality, such as Physics<dim>.

The other use of templates in Yggdrasil is for Field datatypes, as in template <typename T> class Field. This allows methods on the NodeList class that retrieve and store Field data to retrieve any type of Field, as in template <typename T> Field<T>* getField(const std::string& name) const, and Fields can then be used as their templated data types, as in VectorField* position = nodeList->getField<Vector>("position"), where using VectorField = Field<Vector>.

Note

Vector is also a templated class and is in the Lin namespace, and by using Vector = Lin::Vector<dim> within our templated classes, we can ensure that we’re using the correctly dimensioned Vector class throughout without having to invoke Field<Lin::Vector<dim>>* position = nodeList->getField<Lin::Vector<dim>>("position").