A Functional Plus Predicate Logic Programming

The language described in this paper is based on an attempt to combine relational and functional languages in a unified environment, which provides the best features of both approaches. Our goal was to design design a first order logic language, which allows to define both functions and procedures. Our language is a proper extension of functional languages enriched with somewhat constrained Horn clauses. The constraints are concerned with distinguishing between input and output parameter and sequencing of literals