15 research outputs found
Retractions in Intersection Types
This paper deals with retraction - intended as isomorphic embedding - in
intersection types building left and right inverses as terms of a lambda
calculus with a bottom constant. The main result is a necessary and sufficient
condition two strict intersection types must satisfy in order to assure the
existence of two terms showing the first type to be a retract of the second
one. Moreover, the characterisation of retraction in the standard intersection
types is discussed.Comment: In Proceedings ITRS 2016, arXiv:1702.0187
The heart of intersection type assignment: Normalisation proofs revisited
AbstractThis paper gives a new proof for the approximation theorem and the characterisation of normalisability using intersection types for a system with ‘w and a ≤-relation that is contra-variant over arrow types. The technique applied is to define reduction on derivations and to show a strong normalisation result for this reduction. From this result, the characterisation of strong normalisation and the approximation result will follow easily; the latter, in its turn, will lead to the characterisation of (head) normalisability
The Heart of Intersection Type Assignment
This paper gives a new proof for the approximation theorem and the characterisation of normalisability using intersection types. The technique applied is to define reduction on derivations and to show a strong normalisation result for this reduction. From this result, the characterisation of strong normalisation and the approximation result will follow easily; the latter, in its turn, will lead to the characterisation of (head-)normalisability
The Heart of Intersection Type Assignment
This paper gives a new proof for the approximation theorem and the characterisation of normalisability using intersection types. The technique applied is to define reduction on derivations and to show a strong normalisation result for this reduction. From this result, the characterisation of strong normalisation and the approximation result will follow easily; the latter, in its turn, will lead to the characterisation of (head-)normalisability
A type system for context-dependent overloading.
This article presents a type system for context-dependent overloading, based on the notion of constrained types. These are types constrained by the definition of functions or constants of given types. This notion supports both overloading and a form of subtyping, and is related to Haskell type classes [11,2], System O [7] and other systems with constrained types. We study an extension of the Damas-Milner system [4,1] with constrained types. The inference system presented uses a context-dependent overloading policy, which is specified by means of a predicate used in a single inference rule. The idea simplifies the treatment of overloading, enables the simplification of inferred types (by means of class type annotations), and is adequate for use in a type system with higher-order types
On sets of terms having a given intersection type
Working in a variant of the intersection type assignment system of Coppo,
Dezani-Ciancaglini and Venneri [1981], we prove several facts about sets of
terms having a given intersection type. Our main result is that every strongly
normalizing term M admits a *uniqueness typing*, which is a pair
such that
1)
2)
We also discuss several presentations of intersection type algebras, and the
corresponding choices of type assignment rules.
Moreover, we show that the set of closed terms with a given type is uniformly
separable, and, if infinite, forms an adequate numeral system. The proof of
this fact uses an internal version of the B\"ohm-out technique, adapted to
terms of a given intersection type
Essential intersection type assignment
This paper introduces a notion of intersection type assignment on the Lambda Calculus that is a restriction of the BCD-system as presented in [4]. This restricted system is essential in the following sense: it is an almost syntax directed system that satisfies all major properties of the BCD-system. The set of typeable terms can be characterized in the same way, the system is complete with respect to the simple type semantics, and it has the principal type property