Two type extensions for the constraint modelling language MiniZinc

Abstract

In this paper we present two type extensions for the modelling language MiniZinc that allow the representation of some problems in a more natural way. The first proposal, called MiniZinc? , extends existing types with additional values. The user can specify both the extension of a predefined type with new values, and the behavior of the operations with relation to the new types. We illustrate the usage of MiniZinc? to model SQL-like problems with integer variables extended with NULL values. The second extension, MiniZinc+, introduces union types in the language. This allows defining recursive types such as trees, which are very useful for modelling problems that involve complex structures. A new case statement is introduced to select the different components of union type terms. The paper shows how a model defined using these extensions can be transformed into a MiniZinc model which is equivalent to the original model.