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Generic types in C behave invariantly with respect to sub-typing. We propose a system of type-safe variance for C that supports the declaration of covariant and contravariant type parameters on generic types. To support more widespread application of variance we also generalize the existing constraint mechanism with arbitrary subtype assertions on classes(More)
The Microsoft.NET Common Language Runtime provides a shared type system, intermediate language and dynamic execution environment for the implementation and inter-operation of multiple source languages. In this paper we extend it with direct support for parametric polymorphism (also known as generics), describing the design through examples written in an(More)
SML.NET is a compiler for Standard ML that targets the Common Language Runtime and is integrated into the Visual Studio development environment. It supports easy interoperability with other .NET languages via a number of language extensions, which go considerably beyond those of our earlier compiler, MLj.This paper describes the new language extensions and(More)
Generalized algebraic data types (GADTs) have received much attention recently in the functional programming community. They generalize the (type) parameterized algebraic datatypes (PADTs) of ML and Haskell by permitting value constructors to return specific, rather than parametric, type-instantiations of their own datatype. GADTs have a number of(More)
We give a denotational semantics to a type and effect system tracking reading and writing to global variables holding values that may include higher-order effectful functions. Refined types are modelled as partial equivalence relations over a recursively-defined domain interpreting the untyped language, with effect information interpreted in terms of the(More)
This study compares the effectiveness of various image enhancement filters for improving the perceived visibility of coloured digital natural images for people with visual impairment. Generic filters were compared with Peli's adaptive enhancement and adaptive thresholding and custom-devised filters based on each subject's contrast sensitivity loss. Subjects(More)
Scientists and engineers must ensure that physical equations are dimensionally consistent, but existing programming languages treat all numeric values as dimensionless. This paper extends a strongly-typed programming language with a notion of dimension type. Our approach improves on previous proposals in that dimension types may be poly-morphic.(More)