James Leslie Keedy

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Qualifying types represent a new approach to modifying the behaviour of instances of other types in a general way, in the form of components which can be designed and implemented without a prior knowledge of the types to be modified or their implementations. This paper illustrates the idea by showing how they can be used to program various standard(More)
Traditionally, instruction sets have included separate instructions for manipulating different data types, such as integers and real numbers. A long-discussed but seldom-implemented alternative has been tagging, where the type information is stored adjacent to the data itself, rather than being inferred from the instructions. Over the years, several(More)
The system architecture of the ICL 2900 Series is outlined informally. Its central feature, the virtual machine concept, is described and related to virtual storage, segmentation and paging. The procedural approach is then discussed and its implementation by a stack mechanism is described. Further sections outline the protection mechanisms, and the(More)
Inheritance mechanisms are used to express many different programming concepts. In this paper we analyse these inheritance concepts to determine the requirements for an inheritance mechanism which is to support the concepts well. On the basis of this analysis we identify weaknesses in current mechanisms, particularly in the areas of modelling and signature(More)
Unlike most object oriented programming languages Timor, which has been designed to support component development, replaces the class construct with separate constructs for defining types and their implementations (which are not types). It also distinguishes between be-haviourally conforming subtyping and the inclusion of behaviourally deviant interfaces in(More)