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1733 results in Computing: general interest

Page 85 of 87

  • Preface

  • Rohl
  • Book:
    Recursion via Pascal
    Published online:
    05 February 2012
    Print publication:
    26 July 1984, pp ix-x

  • Summary

    Recursion is the Cinderella of programming techniques where languages such as Pascal are concerned. All primers mention it, of course, but generally devote only a few pages to it. Rohl and Barrett's Programming via Pascal is one of the more generous: it contains one chapter of 12 pages on the subject!

    Books appropriate to second courses in programming, such as those by Wirth (1976), Alagic & Arbib (1978), and the more modern data structures texts, have helped considerably; but currently there is no book devoted to the use of recursion in Pascal or similar languages.

    And yet this used not to be the case: Barron's delightful little book Recursive Techniques in Programming was published in 1968! Sadly it is now out of print, and in any event was beginning to show its age. Recursion via Pascal is the author's attempt to fill this gap.

    Of course, in functional programming, recursion has received its full due, since it is quite often the only repetitive construct, and this area is fairly well served with text-books. In Recursion via Pascal, most of the examples are procedures rather than functions, partly because that is the usual Pascal style and partly because we want to give examples which actually do something, like drawing the cover motif of this series, instead of merely having a value. Reading one of the functional texts after finishing this book would provide an alternative perspective.

  • 8 - The elimination of recursion

  • Rohl
  • Book:
    Recursion via Pascal
    Published online:
    05 February 2012
    Print publication:
    26 July 1984, pp 166-189

  • Summary

    We are going to finish our study of recursion in Pascal programming by seeing how to eliminate it. This may seem a curious thing to do given that for seven chapters we have strongly pressed the case for using recursion, but there are a number of reasons for doing so.

    Firstly, it may be that the system we are using does not allow recursion. Such a restriction will not arise with Pascal, of course, but sometimes we are obliged to write in Fortran where such a restriction is part of the language definition. If we can translate a recursive procedure into a non-recursive one, then we can still retain the advantages of designing our programs recursively.

    Secondly, where there are two or more forms of recursion in a procedure, its readability may be improved by the removal of one of the recursive aspects. We discussed this idea in Chapter 2 and used it in Chapters 5 and 6. For improved readability, the recursion to be eliminated must be of the preorder, linear type.

    Thirdly, we may have tight space constraints or very tight time constraints and it may be that the replacement of a recursive procedure by an iterative one allows us to satisfy those constraints.

    Finally, and most importantly, we may wish to consider the elimination of recursion purely to increase our understanding of recursive procedures.

Page 85 of 87