We introduce the notion of a perfect process tree as a model for the full propagation of in forma tion in metacomputation. Starting with constant propagation we construct step-by-step the driving mechanism used in supercompilation which ensures the perfect propagation of information. The concept of a simple supercompiler based on perfect driving coupled with a simple folding strategy is explained. As an example we demonstrate that specializing a naive pattern matcher with respect to a fixed pattern obtains the efficiency of a matcher generated by the Knuth, Morris & Pratt al gorithm.

This paper gives a gentle introduction to Turchin's supercompilation and its applications in metacomputation with an emphasis on recent developments. First, a complete supercompiler, including positive driving and generalization, is defined for a functional language and illustrated with examples. Then a taxonomy of related transformers is given and compared to the supercompiler. Finally, we put supercompilation into the larger perspective of metacomputation and consider three metacomputation tasks: specialization, composition, and inversion.

this paper, semantics modifiers exist for a wide class of computational problems, including non-standard computation, program analysis and

. In recent work, we proposed a simple functional language S-graph-n to study metaprogramming aspects of self-applicable online program specialization. The primitives of the language provide support for multiple encodings of programs. An important component of online program specialization is the termination strategy. In this paper we show that such a representation has the great advantage of simplifying generalization of multiply encoded data. After developing and formalizing the basic metaprogramming concepts, we extend two basic methods to multiply encoded data: most specific generalization and the homeomorphic embedding relation. Examples and experiments with the initial design of an online specializer illustrate their use in hierarchies of online program specializers. 1 Introduction Multiple levels of metaprograms have become an issue for several reasons, on the one hand they are a natural extension of metaprogramming approaches, on the other hand they have been used to great adv...

An approach for systematically modifying the semantics of programming languages by semantics modifiers is described. Semantics modifiers are a class of programs that allow the development of general and reusable "semantics components". Language independence is achieved through the interpretive approach: an interpreter serves as a mediator between the new language and the language for which the non-standard semantics was implemented. Inverse computation, equivalence transformation and neighborhood analysis are shown to be semantics modifiers. Experiments with these modifiers show the computational feasibility of this approach. Seven modifier projections are given which allow the e#cient implementation of non-standard interpreters and non-standard compilers by program specialization or other powerful program transformation methods.