Relative Specification and Transformational Re-Use of Functional Programs

A relative speciication is a collection of laws relating the behaviour of a required new program to that of one or more existing programs. A two stage method for transforming such relative speciications into eeective functional programs is described and illustrated. The inversion stage rearranges the specifying laws to obtain a collection of partial deenitions for each unknown function, typically involving non-deterministic operators. The subsequent fusion stage combines each set of partial deenitions into a single complete deenition, thereby eliminating non-deterministic operators.