7.1 Interface Contracts

Dezyne does not have an exception mechanism like other languages. An exception mechanism is designed to prevent accidentally ignoring missed pre- or post-conditions. Instead, in Dezyne the interfaces establish these restrictions by means of verification (See Formal Verification). So where traditional programming languages must handle protocol violations using an exception mechanism at runtime, Dezyne prevents them using the static verification checks⁸. Interfaces in Dezyne are inherently complete with respect to their event alphabet. The generated code will accept every trigger but give an illegal response.

The illegal response is mapped to std::abort () in C++. Note that for a fully verified Dezyne system, operated by clients that adhere to the interface specifications, it is impossible for an illegal response to be triggered. In other words, when an illegal is triggered, it means that some non-Dezyne code is violating a protocol (interface specification).