Typechecking and modules for multi-methods

  • Authors:

  • Craig Chambers;Gary T. Leavens

  • Affiliations:

  • Department of Computer Science and Engineering, University of Washington;Department of Computer Science, Iowa State University

  • Venue:
  • OOPSLA '94 Proceedings of the ninth annual conference on Object-oriented programming systems, language, and applications
  • Year:
  • 1994

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Abstract

Two major obstacles hindering the wider acceptance of multi-methods are concerns over the lack of encapsulation and modularity and the absence of static typechecking in existing multi-method-based languages. This paper addresses both of these problems. We present a polynomial-time static typechecking algorithm that checks the conformance, completeness, and consistency of a group of method implementations with respect to declared message signatures. This algorithm improves on previous algorithms by handling separate type and inheritance hierarchies, abstract classes, and graph-based method lookup semantics. We also present a module system that enables independently-developed code to be fully encapsulated and statically typechecked on a per-module basis. To guarantee that potential conflicts between independently-developed modules have been resolved, a simple well-formedness condition on the modules comprising a program is checked at link-time. The typechecking algorithm and module system are applicable to a range of multi-method-based languages, but the paper uses the Cecil language as a concrete example of how they can be applied.