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Pict: A programming language based on the picalculus
 PROOF, LANGUAGE AND INTERACTION: ESSAYS IN HONOUR OF ROBIN MILNER
, 1997
"... The πcalculus offers an attractive basis for concurrent programming. It is small, elegant, and well studied, and supports (via simple encodings) a wide range of highlevel constructs including data structures, higherorder functional programming, concurrent control structures, and objects. Moreover ..."
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Cited by 254 (9 self)
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The πcalculus offers an attractive basis for concurrent programming. It is small, elegant, and well studied, and supports (via simple encodings) a wide range of highlevel constructs including data structures, higherorder functional programming, concurrent control structures, and objects. Moreover, familiar type systems for the calculus have direct counterparts in the πcalculus, yielding strong, static typing for a highlevel language using the πcalculus as its core. This paper describes Pict, a stronglytyped concurrent programming language constructed in terms of an explicitlytypedcalculus core language.
The Type and Effect Discipline
 Information and Computation
, 1992
"... The type and effect discipline is a new framework for reconstructing the principal type and the minimal effect of expressions in implicitly typed polymorphic functional languages that support imperative constructs. The type and effect discipline outperforms other polymorphic type systems. Just as ty ..."
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Cited by 153 (3 self)
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The type and effect discipline is a new framework for reconstructing the principal type and the minimal effect of expressions in implicitly typed polymorphic functional languages that support imperative constructs. The type and effect discipline outperforms other polymorphic type systems. Just as types abstract collections of concrete values, effects denote imperative operations on regions. Regions abstract sets of possibly aliased memory locations. Effects are used to control type generalization in the presence of imperative constructs while regions delimit observable sideeffects. The observable effects of an expression range over the regions that are free in its type environment and its type; effects related to local data structures can be discarded during type reconstruction. The type of an expression can be generalized with respect to the variables that are not free in the type environment or in the observable effect. 1 Introduction Type inference [12] is the process that automa...
The Polymorphic Picalculus: Theory and Implementation
, 1995
"... We investigate whether the πcalculus is able to serve as a good foundation for the design and implementation of a stronglytyped concurrent programming language. The first half of the dissertation examines whether the πcalculus supports a simple type system which is flexible enough to provide a su ..."
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Cited by 96 (0 self)
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We investigate whether the πcalculus is able to serve as a good foundation for the design and implementation of a stronglytyped concurrent programming language. The first half of the dissertation examines whether the πcalculus supports a simple type system which is flexible enough to provide a suitable foundation for the type system of a concurrent programming language. The second half of the dissertation considers how to implement the πcalculus efficiently, starting with an abstract machine for πcalculus and finally presenting a compilation of πcalculus to C. We start the dissertation by presenting a simple, structural type system for πcalculus, and then, after proving the soundness of our type system, show how to infer principal types for πterms. This simple type system can be extended to include useful typetheoretic constructions such as recursive types and higherorder polymorphism. Higherorder polymorphism is important, since it gives us the ability to implement abstract datatypes in a typesafe manner, thereby providing a greater degree of modularity for πcalculus programs. The functional computational paradigm plays an important part in many programming languages. It is wellknown that the πcalculus can encode functional computation. We go further and show that the type structure of λterms is preserved by such encodings, in the sense that we can relate the type of a λterm to the type of its encoding in the πcalculus. This means that a πcalculus programming language can genuinely support typed functional programming as a special case. An efficient implementation of πcalculus is necessary if we wish to consider πcalculus as an operational foundation for concurrent programming. We first give a simple abstract machine for πcalculus and prove it correct. We then show how this abstract machine inspires a simple, but efficient, compilation of πcalculus to C (which now forms the basis of the Pict programming language implementation).
What Are Principal Typings and What Are They Good For?
, 1995
"... We demonstrate the pragmatic value of the principal typing property, a property more general than ML's principal type property, by studying a type system with principal typings. The type system is based on rank 2 intersection types and is closely related to ML. Its principal typing property ..."
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Cited by 93 (0 self)
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We demonstrate the pragmatic value of the principal typing property, a property more general than ML's principal type property, by studying a type system with principal typings. The type system is based on rank 2 intersection types and is closely related to ML. Its principal typing property provides elegant support for separate compilation, including "smartest recompilation" and incremental type inference, and for accurate type error messages. Moreover, it motivates a novel rule for typing recursive definitions that can type many examples of polymorphic recursion.
Coinductive Axiomatization of Recursive Type Equality and Subtyping
, 1998
"... e present new sound and complete axiomatizations of type equality and subtype inequality for a firstorder type language with regular recursive types. The rules are motivated by coinductive characterizations of type containment and type equality via simulation and bisimulation, respectively. The mai ..."
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Cited by 66 (2 self)
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e present new sound and complete axiomatizations of type equality and subtype inequality for a firstorder type language with regular recursive types. The rules are motivated by coinductive characterizations of type containment and type equality via simulation and bisimulation, respectively. The main novelty of the axiomatization is the fixpoint rule (or coinduction principle), which has the form A; P ` P A ` P (Fix) where P is either a type equality = 0 or type containment 0 and the proof of the premise must be contractive in a formal sense. In particular, a proof of A; P ` P using the assumption axiom is not contractive. The fixpoint rule embodies a finitary coinduction principle and thus allows us to capture a coinductive relation in the fundamentally inductive framework of inference systems. The new axiomatizations are more concise than previous axiomatizations, particularly so for type containment since no separate axiomatization of type equality is required, as in A...
Efficient Multilevel Generating Extensions for Program Specialization
, 1995
"... . Multiple program specialization can stage a computation into several computation phases. This paper presents an effective solution for multiple program specialization by generalizing conventional offline partial evaluation and integrating the "cogen approach" with a multilevel binding ..."
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Cited by 59 (5 self)
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. Multiple program specialization can stage a computation into several computation phases. This paper presents an effective solution for multiple program specialization by generalizing conventional offline partial evaluation and integrating the "cogen approach" with a multilevel bindingtime analysis. This novel "multicogen approach" solves two fundamental problems of selfapplicable partial evaluation: the generationtime problem and the generatorsize problem. The multilevel program generator has been implemented for a higherorder subset of Scheme. Experimental results show a remarkable reduction of generation time and generator size compared to previous attempts of multiple selfapplication. 1 Introduction Stages of computation arise naturally in many programs, depending on the availability of data or the frequency with which the input changes. Code for later stages can be optimized based on values available in earlier stages. Partial evaluation has received much attention beca...
Recursive Subtyping Revealed
 Journal of Functional Programming
, 2000
"... Algorithms for checking subtyping between recursive types lie at the core of many programming language implementations. But the fundamental theory of these algorithms and how they relate to simpler declarative specifications is not widely understood, due in part to the difficulty of the available in ..."
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Cited by 38 (4 self)
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Algorithms for checking subtyping between recursive types lie at the core of many programming language implementations. But the fundamental theory of these algorithms and how they relate to simpler declarative specifications is not widely understood, due in part to the difficulty of the available introductions to the area. This tutorial paper offers an "endtoend" introduction to recursive types and subtyping algorithms, from basic theory to efficient implementation, set in the unifying mathematical framework of coinduction. 1. INTRODUCTION Recursively defined types in programming languages and lambdacalculi come in two distinct varieties. Consider, for example, the type X described by the equation X = Nat!(Nat\ThetaX): An element of X is a function that maps a number to a pair consisting of a number and a function of the same form. This type is often written more concisely as X.Nat!(Nat\ThetaX). A variety of familiar recursive types such as lists and trees can be defined analogou...
Safe polymorphic type inference for a dynamically typed language: translating scheme to ml, in
 Proceedings of the seventh international conference on Functional programming languages and computer architecture, FPCA ’95, ACM
, 1995
"... We describe a new method for polymorphic type inference for the dynamically typed language Scheme. The method infers both types and explicit run time type operations (coerc!ons) for a given program. It can be used to statically debug Scheme programs and to give a highlevel translation to ML, in es ..."
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Cited by 30 (0 self)
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We describe a new method for polymorphic type inference for the dynamically typed language Scheme. The method infers both types and explicit run time type operations (coerc!ons) for a given program. It can be used to statically debug Scheme programs and to give a highlevel translation to ML, in essence providing an “embedding ” of Scheme into ML. Our method combines the following desirable properties:
An Automatic Program Generator for MultiLevel Specialization
 LISP AND SYMBOLIC COMPUTATION
, 1997
"... Program specialization can divide a computation into several computation stages. This paper investigates the theoretical limitations and practical problems of standard specialization tools, presents multilevel specialization, and demonstrates that, in combination with the cogen approach, it is far ..."
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Cited by 28 (4 self)
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Program specialization can divide a computation into several computation stages. This paper investigates the theoretical limitations and practical problems of standard specialization tools, presents multilevel specialization, and demonstrates that, in combination with the cogen approach, it is far more practical than previously supposed. The program generator which we designed and implemented for a higherorder functional language converts programs into very compact multilevel generating extensions that guarantee fast successive specialization. Experimental results show a remarkable reduction of generation time and generator size compared to previous attempts of multilevel specialization by selfapplication. Our approach to multilevel specialization seems wellsuited for applications where generation time and program size are critical.