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31
Putting Type Annotations to Work
, 1996
"... We study an extension of the HindleyMilner system with explicit type scheme annotations and type declarations. The system can express polymorphic function arguments, userdefined data types with abstract components, and structure types with polymorphic fields. More generally, all programs of the po ..."
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Cited by 94 (1 self)
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We study an extension of the HindleyMilner system with explicit type scheme annotations and type declarations. The system can express polymorphic function arguments, userdefined data types with abstract components, and structure types with polymorphic fields. More generally, all programs of the polymorphic lambda calculus can be encoded by a translation between typing derivations. We show that type reconstruction in this system can be reduced to the decidable problem of firstorder unification under a mixed prefix.
Mixin Modules
, 1996
"... Mixin modules are proposed as a new construct for module languages, allowing recurslye definitions to span module boundaries. Mixin modules are proposed specifically for the Standard ML language. Several applications are described, including the resolution of cycles in module import dependency graph ..."
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Cited by 60 (2 self)
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Mixin modules are proposed as a new construct for module languages, allowing recurslye definitions to span module boundaries. Mixin modules are proposed specifically for the Standard ML language. Several applications are described, including the resolution of cycles in module import dependency graphs, as well as functionality related to Haskell type classes and CLOS generic functions, though without any complications to the core language semantics. Mixin modules require no changes to the core ML type system, and only a very minor change to its runtime semantics. A type system and reduction semantics are provided, and the former is verified to be sound relative to the latter.
Objective ML: An effective objectoriented extension to ML
 THEORY AND PRACTICE OF OBJECT SYSTEMS
, 1998
"... Objective ML is a small practical extension to ML with objects and top level classes. It is fully compatible with ML; its type system is based on ML polymorphism, record types with polymorphic access, and a better treatment of type abbreviations. Objective ML allows for most features of objectorien ..."
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Cited by 55 (4 self)
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Objective ML is a small practical extension to ML with objects and top level classes. It is fully compatible with ML; its type system is based on ML polymorphism, record types with polymorphic access, and a better treatment of type abbreviations. Objective ML allows for most features of objectoriented languages including multiple inheritance, methods returning self and binary methods as well as parametric classes. This demonstrates that objects can be added to strongly typed languages based on ML polymorphism.
An Interpretation of Objects and Object Types
, 1996
"... We present an interpretation of typed objectoriented concepts in terms of wellunderstood, purely procedural concepts. More precisely, we give a compositional subtypepreserving translation of a basic object calculus supporting method invocation, functional method update, and subtyping, into the pol ..."
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Cited by 51 (1 self)
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We present an interpretation of typed objectoriented concepts in terms of wellunderstood, purely procedural concepts. More precisely, we give a compositional subtypepreserving translation of a basic object calculus supporting method invocation, functional method update, and subtyping, into the polymorphic calculus with recursive types and subtyping. The translation techniques apply also to an imperative version of the object calculus which includes inplace method update and object cloning. Finally, the translation easily extends to "Self types" and other interesting objectoriented constructs. 1 Introduction Objectoriented programming languages have introduced numerous ideas, structures, and techniques. Although these contributions are not always conceptually clear (or even sound), they are often original and useful. One of the most basic contributions is the notion of self; the operations associated with an object (its methods) can refer to the object as self, and invoke other op...
Firstclass Polymorphism with Type Inference
"... Languages like ML and Haskell encourage the view of values as firstclass entities that can be passed as arguments or results of functions, or stored as components of data structures. The same languages o#er parametric polymorphism, which allows the use of values that behave uniformly over a range ..."
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Cited by 47 (0 self)
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Languages like ML and Haskell encourage the view of values as firstclass entities that can be passed as arguments or results of functions, or stored as components of data structures. The same languages o#er parametric polymorphism, which allows the use of values that behave uniformly over a range of di#erent types. But the combination of these features is not supported polymorphic values are not firstclass. This restriction is sometimes attributed to the dependence of such languages on type inference, in contrast to more expressive, explicitly typed languages, like System F, that do support firstclass polymorphism. This paper uses relationships between types and logic to develop a type system, FCP, that supports firstclass polymorphism, type inference, and also firstclass abstract datatypes. The immediate result is a more expressive language, but there are also long term implications for language design. 1
Programming Languages for Reusable Software Components
, 1999
"... Programming languages offer a variety of constructs to support code reuse. For example, functional languages provide function constructs for encapsulating expressions to be used in multiple contexts. Similarly, objectoriented languages provide class (or classlike) constructs for encapsulating sets ..."
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Cited by 25 (0 self)
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Programming languages offer a variety of constructs to support code reuse. For example, functional languages provide function constructs for encapsulating expressions to be used in multiple contexts. Similarly, objectoriented languages provide class (or classlike) constructs for encapsulating sets of definitions that are easily adapted for new programs. Despite the variety and abundance of such programming constructs, however, existing languages are illequipped to support component programming with reusable software components. Component programming differs from other forms of reuse in its emphasis on the independent development and deployment of software components. In its ideal form, component programming means building programs from offtheshelf components that are supplied by a softwarecomponents industry. This model suggests a strict separation between the producer and consumer of a component. The separation, in turn, implies separate compilation for components, allowing a pr...
ConstraintBased Type Inference for Guarded Algebraic Data Types
, 2003
"... Guarded algebraic data types, which subsume the concepts known in the literature as indexed types, guarded recursive datatype constructors, and phantom types, and are closely related to inductive types, have the distinguishing feature that, when typechecking a function defined by cases, every branch ..."
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Cited by 25 (3 self)
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Guarded algebraic data types, which subsume the concepts known in the literature as indexed types, guarded recursive datatype constructors, and phantom types, and are closely related to inductive types, have the distinguishing feature that, when typechecking a function defined by cases, every branch must be checked under di#erent typing assumptions. This mechanism allows exploiting the presence of dynamic tests in the code to produce extra static type information.
A constraintbased approach to guarded algebraic data types
 ACM Trans. Prog. Languages Systems
, 2007
"... We study HMG(X), an extension of the constraintbased type system HM(X) with deep pattern matching, polymorphic recursion, and guarded algebraic data types. Guarded algebraic data types subsume the concepts known in the literature as indexed types, guarded recursive datatype constructors, (firstcla ..."
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Cited by 24 (0 self)
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We study HMG(X), an extension of the constraintbased type system HM(X) with deep pattern matching, polymorphic recursion, and guarded algebraic data types. Guarded algebraic data types subsume the concepts known in the literature as indexed types, guarded recursive datatype constructors, (firstclass) phantom types, and equality qualified types, and are closely related to inductive types. Their characteristic property is to allow every branch of a case construct to be typechecked under different assumptions about the type variables in scope. We prove that HMG(X) is sound and that, provided recursive definitions carry a type annotation, type inference can be reduced to constraint solving. Constraint solving is decidable, at least for some instances of X, but prohibitively expensive. Effective type inference for guarded algebraic data types is left as an issue for future research.
TypeTheoretic Methodology For Practical Programming Languages
 DEPARTMENT OF COMPUTER SCIENCE, CORNELL UNIVERSITY
, 1998
"... The significance of type theory to the theory of programming languages has long been recognized. Advances in programming languages have often derived from understanding that stems from type theory. However, these applications of type theory to practical programming languages have been indirect; the ..."
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Cited by 22 (3 self)
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The significance of type theory to the theory of programming languages has long been recognized. Advances in programming languages have often derived from understanding that stems from type theory. However, these applications of type theory to practical programming languages have been indirect; the differences between practical languages and type theory have prevented direct connections between the two. This dissertation presents systematic techniques directly relating practical programming languages to type theory. These techniques allow programming languages to be interpreted in the rich mathematical domain of type theory. Such interpretations lead to semantics that are at once denotational and operational, combining the advantages of each, and they also lay the foundation for formal verification of computer programs in type theory. Previous type theories either have not provided adequate expressiveness to interpret practical languages, or have provided such expressiveness at the expense of essential features of the type theory. In particular, no previous type theory has supported a notion of partial functions (needed to interpret recursion in practical languages), and a notion of total functions and objects (needed to reason about data values), and an intrinsic notion of equality (needed for most interesting results). This dissertation presents the first type theory incorporating all three, and discusses issues arising in the design of that type theory. This type theory is used as the target of a typetheoretic semantics for a expressive programming calculus. This calculus may serve as an internal language for a variety of functional programming languages. The semantics is stated as a syntaxdirected embedding of the programming calculus into type theory. A critical point arising in both the type theory and the typetheoretic semantics is the issue of admissibility. Admissibility governs what types it is legal to form recursive functions over. To build a useful type theory for partial functions it is necessary to have a wide class of admissible types. In particular, it is necessary for all the types arising in the typetheoretic semantics to be admissible. In this dissertation I present a class of admissible types that is considerably wider than any previously known class.
SemiExplicit FirstClass Polymorphism for ML
 Information and Computation
, 1999
"... We propose a modest conservative extension to ML that allows semiexplicit firstclass polymorphism while preserving the essential properties of type inference. In our proposal, the introduction of polymorphic types is fully explicit, that is, both introduction points and exact polymorphic types ..."
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Cited by 20 (1 self)
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We propose a modest conservative extension to ML that allows semiexplicit firstclass polymorphism while preserving the essential properties of type inference. In our proposal, the introduction of polymorphic types is fully explicit, that is, both introduction points and exact polymorphic types are to be specified. However, the elimination of polymorphic types is semiimplicit: only elimination points are to be specified as polymorphic types themselves are inferred. This extension is particularly useful in Objective ML where polymorphism replaces subtyping. Introduction The success of the ML language is due to its combination of several attractive features. Undoubtedly, the polymorphism of ML [Damas and Milner, 1982] or polymorphism `a la ML with the type inference it allows, is a major advantage. The ML type system stays in close correspondence with the rules of logic, following the CurryHoward isomorphism between types and formulas, which provides a simple intuition, ...