Technical Report 2014-015

Subtyping, consistency and derivability

Sven-Olof Nyström

May 2014


Earlier work on subtyping has focused on the problem of constructing a typing for a given program. This paper considers a slightly different problem: Given a lambda term, is the corresponding constraint system consistent? An O(n3) algorithm for checking the consistency of constraint systems is presented, where n is the size of the constraint system.

The paper also considers the problem of derivability, i.e., whether a property can be derived from the corresponding constraint system and gives an O(n3) algorithm for checking derivability of a class of constraints.

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