Tacit definition
Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. ~ 1991 ACM 0-89791 -441-4/91 /0008/0202 ...$1 .50
Simplifying array processing languages
A language like APL was a masterpiece of simplification when seen through the eyes of a computer user of the seventies. The virtues of simplicity are usually held to be many.This paper firstly discusses simplicity in general, reviews some of the writing on simplicity coming from the computing world, and briefly construes the development of APL, and the later J, as being essentially efforts in simplification. Possibilities for further simplification are then canvassed.Firstly, simplification of the usually accepted but unfortunate naming conventions adopted by array processing languages is proposed. Secondly, simplification of the arithmetic is very briefly outlined, more detailed treatment of this topic being available elsewhere. Thirdly, syntactic means for having all functions and operations dyadic are treated, and the advantages of adopting such means evaluated. Fourthly, the possibilities for a newly distinctive kind of function (called extractions) are described. These are considered as a kind of systematic renaming to supply arguments to functions. Fifthly, and in the context of J's simplifications, the need for hyperoperators is asserted. Finally, the nature of interpreters for array processing languages is reviewed, and suggestions made for facilities to be provided by such interpreters to aid the process of developing array processing code.
Correlation of the Upper Cretaceous White Chalk (Turonian to Campanian) in the Anglo-Paris Basin
Using key lithological, biostratigraphic and geophysical borehole-log markers a correlation of the Upper Cretaceous Chalk stratigraphies across the whole Anglo-Paris Basin has been achieved. A common lithological marker bed stratigraphy applies and key fossil markers (inoceramids, Micraster and Echinocorys ) are consistently related to the same lithological markers throughout the basin. The major lithological changes consistently occur at the same levels but are not necessarily equally strongly developed. The magnificent dip section along the French Channel coast between the Somme and the Seine, and the inland sections at Precy-sur-Oise and Verlin (Loiret) illustrate the influence of long-lived tectonic lines on Chalk sedimentation history recognised by: (i) rapid thickness variations; (ii) channel flooring hardgrounds and associated anomalous bedding dips: (iii) stratigraphically anomalous infills of channels which may be metres to kilometres across; (iv) redeposited chalks containing abundant Bathichnus paramoudrae ; (v) tectonically induced slumps and slides with flint and chalk shatter beds (palaeoseismic horizons). These features are found along may axes including the Anticlinal du Bray at Precy and Dieppe, the Anticlinal de Margny-les-Compiegne at Nourard le-Franc and Le Treport (the Bresle Valley Axis) and the Fecamp and Verlin fault systems. The ‘events’ recognised along these axes link with similar events recognised in Sussex (e.g. Kingston Anticline), on Portsdown, at Culver Cliff, Isle of Wight (Sandown Pericline) and on the Weymouth Anticline (White Nothe). Such events are common in the high Turonian, low Coniacian, basal Santonian, and the low and mid Campanian. The recurrence of key marker beds dominated by a particular trace fossil association or sequence, Bathichnus-Thalassinoides suevicus-Zoophycos associated with major changes in lithology, micro and macro-fauna indicates more widespread ‘oceanographic’ cycles of transgression and regression related to Atlantic opening.