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Total unfolding: theory and applications

Part of: JFP Research Articles

Published online by Cambridge University Press:  07 November 2008

Björn Lisper
Björn Lisper
Affiliation:
The Royal Institute of Technology, Department of Teleinformatics, Electrum/204, S-164 40 Kista, Sweden and Swedish Institute of Computer Science, PO Box 1263, S-164 28 Kista, Sweden
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Abstract

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Unfolding is a common technique in program transformations. Here, we present a computation model where unfolding is a simple generalisation of the usual concept of evaluation. The model is a variant of the well-known full substitution evaluation rule for recursive programs. The evaluation mechanism involved is symbolic substitution of function definitions followed by simplification. Simplification is expressed as a confluent rewrite strategy which uses three kinds of reductions: β-reduction, non-erasing reduction, and erasing reduction. Non-erasing reductions include simplification of constant subexpressions. Erasing reductions formalize the behaviour of nonstrict operations. In this computation model, we prove a termination theorem of symbolic unfolding relative to more instantiated calls. A possible application of the model is a technique called total unfolding, where a partially instantiated function call is unfolded until no more calls exist. Under certain conditions the result will be a first order term: such terms correspond to basic blocks in imperative programs and can be efficiently implemented by scheduling techniques. Possible applications are hardware synthesis, and code generation for parallel machines.

Type
Articles
Information
Journal of Functional Programming , Volume 4 , Issue 4 , October 1994 , pp. 479 - 498
Copyright
Copyright © Cambridge University Press 1994

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