Recent functional logic languages such as Curry and Toy combine lazy
functional programming with logic programming features including
logic variables, non-determinism, unification, narrowing, fair search,
concurrency, and residuation. In this paper, we show how to
extend a conventional interpreter for a lazy functional language to
handle these features by adding support for reference cells, process-like
and thread-like concurrency mechanisms, and a novel form of multi-versioned
store.  Our interpretation scheme
is practical, and can be easily extended to perform compilation.
The language specified by our interpreter is designed so that programs 
are deterministic in a novel and useful sense.