In this talk we discuss some general principles of declarative programming before showing the advantages of amalgamating the most important features of declarative programming in a single programming language. The combination of functional and logic programming principles supports the precise formulation of problem specifications. These do not only express the programmer’s intention but are also executable so that they can be used in application programming. Thanks to the strong mathematical foundation of declarative languages, they facilitate methods to analyze and verify programs.

We demonstrate these general ideas with the declarative multi-paradigm language Curry (curry-lang.org). We survey the design and properties of Curry and also discuss tools to analyze various aspects of Curry programs, like the verification of contracts at compile time and the inference of sufficient conditions to ensure the absence of run-time failures.

Michael Hanus studied computer science at the University of Dortmund and received his Ph.D. in 1988. He had research positions at the University of Dortmund, University of Bielefeld, and the Max-Planck Institute for Informatics in Saarbrücken, before he became professor at the RWTH Aachen. Since 2000 he is full Professor of Computer Science at the Kiel University where he leads the research group on Programming Languages and Compiler Construction.

His research activities are mainly concerned with the integration of functional and logic programming languages, the design and implementation of declarative programming languages, type systems for logic languages, analysis and verification techniques for declarative programs, programming environments and applications of declarative programming. He has published more than two hundred papers on these topics in international conference proceedings, journals and books. He was the PC chair of more than a dozen conferences. He is involved in the design, implementation, and application of the multi-paradigm declarative language Curry where he had several nationally and internationally funded research projects.