Applying traits to the smalltalk collection classes

ABSTRACT

Traits are a programming language technology that promote the reuse of methods between unrelated classes. This paper reports on a refactoring of the Smalltalk collections classes using traits. The original collection classes contained much duplication of code; traits let us remove all of it. We also found places where the protocols of the collections lacked uniformity; traits allowed us to correct these non-uniformities without code duplication.Traits also make it possible to reuse fragments of collection code outside of the existing hierarchy; for example, they make it easy to convert other collection-like things into true collections. Our refactoring reduced the number of methods in the collection classes by approximately 10 per cent. More importantly, understandability maintainability and reusability of the code were significantly improved.

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INDEX TERMS

Primary Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.3 Language Constructs and Features
          Subjects: Classes and objects

Additional Classification:
  D. Software
  D.2 SOFTWARE ENGINEERING
      D.2.3 Coding Tools and Techniques
          Subjects: Object-oriented programming

General Terms:
Design, Languages

Keywords:
collection hierarchy, inheritance, mixins, multiple Inheritance, refactoring, reuse, smalltalk, stream classes, traits