Logical Structure Specification and data type definition

Abstract

We describe a constructive approach to the specification of data types. The primary motivation for this approach, which is referred to as the Logical Structure Operation Specification (LSOS), is to highlight certain aspects of a data type, and to possibly suggest one or more implementations for the data type.A key feature of the LSOS is its flexibility, which permits a wide variety of specifications for a data type.This allows the specifier of a data type to communicate to the user any view or perspective which was taken in developing the data type.

Programming with generators

“…Consider input streams of records defined by the following key sequences Runs from the input streams are merged to produce output runs. Thus (5,7) and (2,9,11) yield (2,5,7,9,11) We propose three tag values for a generator that delivers data from the input stream: N(ormal), H(old), and F(inished). T h e tag value is H after the generator has delivered the last item of a run, unless this is the last item of the entire input stream, in which case the value is F. Let us now assume that the generator has a state.…”