Contents

• 1  Introduction

• Part I  An algorithm for detecting the anomalies
  • 2  Patterns, values, etc.
  • 3  The useful clause problem
    • 3.1  Solving the useful clause problem
    • 3.2  Detecting the anomalies
  • 4  Lazy pattern matching
    • 4.1  Lazy pattern matching in theory
    • 4.2  Lazy pattern matching, à la Laville
    • 4.3  Pattern matching in Haskell
    • 4.4  Or-patterns in Haskell
• Part II  Implementation
  • 5  Specializing U for exhaustiveness check
  • 6  Specializing U for the useless clause problem
    • 6.1  Useless clause is (almost) enough
    • 6.2  Expansion of or-patterns
    • 6.3  Rules for finding  useless patterns
    • 6.4  Computation of useless patterns
  • 7  Performance
    • 7.1  Elements of complexity analysis
    • 7.2  Safeguards
    • 7.3  Measures
  • 8  Conclusion
  • A  Series of examples