Writing a Visitor

To avoid assuming a particular set of operations WTF relies on the visitor pattern. This page should eventually be a tutorial, but for now is just a set of notes.

Assume that visitor is an object of type T. The dispatch function will additionally require a std::tuple<FPList...> where FPList... is a list of the floating-point types you want to be able to support. Then assume we are trying to dispatch based on the wrapped types of N FloatBuffer objects.

• T must be a callable type, i.e., define operator(). Functions, lambdas, and functors all satisfy this criterion

• operator() may be overloaded. If it is overloaded, the usual C++ overload

  resolution rules will be used to select the appropriate overload.

• Dispatching considers the type of the floating point buffers and the number of

  floating point buffers.

• operator() overloads must accent N parameters.

• operator() must possess an overload capable of supporting any permutation with replacement of the types in FPLists....

  • The easiest way to satisfy this is to have a templated overload with N template parameters (one for the type of each positional argument).

• Each FloatBuffer will be unwrapped to a std::span<U> object where U is the type of the wrapped floating point objects.