Approaching classical algorithms in APL2

Abstract

Classical algorithms and data structures as made popular by D.E. Knuth's "The Art of Computer Programming" have been largely ignored so far by APL2-programmers. This scepsis was understandable to a certain degree in the era of APL, but has lost its justification with the rise of APL2 and similar APL-successors. First the essence of classical algorithms as well as the principal ways of data structuring and accessing are reexamined. Then it is shown how pseudocodes or implementations of classical algorithms can be transfered one-to-one into APL2 almost automatically and often with an acceptable resulting performance. But, in general, the better way consists in maintaining only the general design principle behind a classical algorithm and combining it with the elegant and efficient specific possibilities of APL2. Both approaches are explained and illustrated by means of a typical classical algorithm from picture processing.