Specifying function specializations over an arbitrary set of type constraints is a daunting task in C++ as soon as those constraints become more and more complex and/or grow in number. Various idioms are traditionally used to solve this problem: SFINAE or Tag Dispatching for example.
This talk introduces Boost.Dispatch, an infrastructure library that make Tag Dispatching easier to use and maintain by providing a protocol to define Tags and relationship between them, to map an arbitrary set of tags to a given function implementation and to extend said list of specialization in an open, modular way. The main new asset of Boost.Dispatch is the ability to use categorization of function properties and/or architectural information to guide the dispatch in addition to the more traditional use of type properties.
The talk will quickly brushes a picture of what SFINAE, overloading and Tag Dispatching mean in C++ and what are their limitations. We’ll introduce Boost.Dispatch over some examples ranging from simple library design to actual high performance computing code using the library to select best implementation of a function based on non-trivial architecture dependent information. Then we’ll dive into the implementation of the library and try to sketches the upcoming challenges yet to be solved.