Transformational programming is a relatively new programming technique intended to derive complex algorithms automatically.Initially, a set of transformational rules is described, and an initial specification of the problem to be programmed is given.The specification is written in a high-level language in a fairly compact form possibly ignoring efficiency.A number of versions, called transformations, are created by successively applying the transformational rules starting with the initial specification.As an example of the application of this technique to a fairly complex case, a transformational derivation of a variant of a known efficient garbage collection and compaction algorithm from an initial very high-level specification is given.Currently, the techniques are still being developed, and therefore the transformations are derived manually.However, most of the transformations done are of a technical nature and could eventually be automated.

“Pure” SETL is a language of very high level allowing algorithms to be programmed rapidly and succintly. SETL's representation sublanguage adds a system of declarations which allow the user of the language to control the data structures that will be used to implement an algorithm which has already been written in pure SETL, so as to improve its efficiency. Ideally no rewriting of the algorithm should be necessary. The facilities provided by the representation sublanguage and the run-time data structures that it can generate are described; based on this a heuristic which uses some of the methods of global program analysis and which should be capable of selecting an acceptably efficient representation automatically is given.

Abstract A fast and compact compiler/interpreter for SPITBOL (a variant of SNOBOL4) has been written in a machine‐independent macro assembly language and implemented initially on the ICL 1900 range of computers. The interpreter uses a novel form of indirect polish code which assists portability. Compile‐time pre‐evaluation of constant expressions has proved to be a worthwhile optimization. A description is given in some detail of the simple but rapid scheme, requiring no marker bits, employed for garbage collection.