Operator Overloading in Modelica 3.1

The constructor and operator overloading introduced in Modelica 3.1 is discussed. The goal is that elementary operators like “+” or “*” can be overloaded for records. This makes it possible to define and use, in a convenient way, complex numbers, polynomials, transfer functions, state space systems, etc. The chosen approach is different to other languages: (a) Only scalar operations need to be overloaded. Array operations are then automatically available, so the growth of the number of overloaded functions is avoided. (b) Automatic type casts between different data types is performed using overloaded constructor functions. Again this reduces the number of overloaded functions. (c) The approach is conservative and only allows overloading if no ambiguity is present, in order to not introduce pitfalls into the language. This is reached by basing the overloading on disjoint sets of matching functions and not on a priority match.