Integrating Constraints into an Imperative Programming Language

We investigate here how to integrate constraints directly into the imperative programming paradigm, as "first class citizens" and not by means of an external library. To this end we provide a systematic account of the issues that arise. In particular, we discuss the role of the logical and customary variables, the interaction between the constraint store and the program, and the need for lists. These considerations lead to an extension of an imperative programming language that supports declarative programming, called Alma-0, introduced in Apt, Brunekreef, Partington & Schaerf (1998). Constraint programs written in this style are simple to understand and analyze