* They are used to represent a functor with a given number of parameters and
* a specific return type. To prevent passing the wrong number of parameters
* and have the compiler detect this error at build-time, each class is numbered
* They are used to represent a functor with a given number of parameters and
* a specific return type. To prevent passing the wrong number of parameters
* and have the compiler detect this error at build-time, each class is numbered