automatic subtyping/intensions

Laurent Martelli
09 Feb 1999 09:54:42 +0100

>>>>> "Tril" == Tril  <> writes:

    >> 1 - B. Liskov and J. Wing: "A Behavioral Notion of Subtyping",
    >> ACM Transactions on Programming Languages and Systems, Number
    >> 16(6), pp. 1811-1841, ACM Press, 1994.

    Tril> Could you summarize the content of the article?  What is
    Tril> meant by a "behavioral notion?"

It means that a type A is a subtype of B if objects of type A behave
exactly the same way as objects of type B. This is the LSP (Liskov
Substitution Principle) : if a function says it wants an argument of
type B, you can give it an object of type A, and it wont see the
difference. This definition does not rely on the name of understood
messages but rather on their semantic.