Unlimp uniqueness as a leitmotiv for implementation

  • Stefan Kahrs
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 631)


When evaluation in functional programming languages is explained using λ-calculus and/or term rewriting systems, expressions and function definitions are often defined as terms, that is as trees. Similarly, the collection of all terms is defined as a forest, that is a directed, acyclic graph where every vertex has at most one incoming edge. Concrete implementations usually drop the last restriction (and sometimes acyclicity as well), i.e. many terms can share a common subterm, meaning that different paths of subterm edges reach the same vertex in the graph.

Any vertex in such a graph represents a term. A term is represented uniquely in such a graph if there are no two different vertices representing it. Such a representation can be established by using hashconsing for the creation of heap objects. We investigate the consequences of adopting uniqueness in this sense as a leitmotiv for implementation (called Unlimp), i.e. not allowing any two different vertices in a graph to represent the same term.


Garbage Collection Graph Reduction Pairing Program Programming Style Functional Programming Language 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1992

Authors and Affiliations

  • Stefan Kahrs
    • 1
  1. 1.Laboratory for Foundations of Computer ScienceUniversity of EdinburghUK

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