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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 283 (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.
Functional Reactive Animation
, 1997
"... Fran (Functional Reactive Animation) is a collection of data types and functions for composing richly interactive, multimedia animations. The key ideas in Fran are its notions of behaviors and events. Behaviors are timevarying, reactive values, while events are sets of arbitrarily complex condition ..."
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Cited by 279 (30 self)
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Fran (Functional Reactive Animation) is a collection of data types and functions for composing richly interactive, multimedia animations. The key ideas in Fran are its notions of behaviors and events. Behaviors are timevarying, reactive values, while events are sets of arbitrarily complex conditions, carrying possibly rich information. Most traditional values can be treated as behaviors, and when images are thus treated, they become animations. Although these notions are captured as data types rather than a programming language, we provide them with a denotational semantics, including a proper treatment of real time, to guide reasoning and implementation. A method to e#ectively and efficiently perform event detection using interval analysis is also described, which relies on the partial information structure on the domain of event times. Fran has been implemented in Hugs, yielding surprisingly good performance for an interpreterbased system. Several examples are given, including the ability to describe physical phenomena involving gravity, springs, velocity, acceleration, etc. using ordinary di#erential equations.
The Marriage of Effects and Monads
, 1998
"... this paper is to marry effects to monads, writing T for a computation that yields a value in and may have effects delimited by oe. Now we have that ( is ..."
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Cited by 120 (7 self)
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this paper is to marry effects to monads, writing T for a computation that yields a value in and may have effects delimited by oe. Now we have that ( is
Forms/3: A FirstOrder Visual Language to Explore the Boundaries of the Spreadsheet Paradigm
"... Although detractors of functional programming sometimes claim that functional programming is too difficult or counterintuitive for most programmers to understand and use, evidence to the contrary can be found by looking at the popularity of spreadsheets. The spreadsheet paradigm, a firstorder subs ..."
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Cited by 119 (40 self)
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Although detractors of functional programming sometimes claim that functional programming is too difficult or counterintuitive for most programmers to understand and use, evidence to the contrary can be found by looking at the popularity of spreadsheets. The spreadsheet paradigm, a firstorder subset of the functional programming paradigm, has found wide acceptance among both programmers and end users. Still, there are many limitations with most spreadsheet systems.
Tackling the awkward squad: monadic input/output, concurrency, exceptions, and foreignlanguage calls in Haskell
 Engineering theories of software construction
, 2001
"... Functional programming may be beautiful, but to write real applications we must grapple with awkward realworld issues: input/output, robustness, concurrency, and interfacing to programs written in other languages. These lecture notes give an overview of the techniques that have been developed by th ..."
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Cited by 113 (1 self)
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Functional programming may be beautiful, but to write real applications we must grapple with awkward realworld issues: input/output, robustness, concurrency, and interfacing to programs written in other languages. These lecture notes give an overview of the techniques that have been developed by the Haskell community to address these problems. I introduce various proposed extensions to Haskell along the way, and I offer an operational semantics that explains what these extensions mean. This tutorial was given at the Marktoberdorf Summer School 2000. It will appears in the book “Engineering theories of software construction, Marktoberdorf Summer School 2000”, ed CAR Hoare, M Broy, and R Steinbrueggen, NATO ASI Series, IOS Press, 2001, pp4796. This version has a few errors corrected compared with the published version. Change summary: Apr 2005: some examples added to Section 5.2.2, to clarifyevaluate. March 2002: substantial revision 1
How to Declare an Imperative
, 1995
"... How can we integrate interaction into a purely declarative language? This tutorial describes a solution to this problem based on a monad. The solution has been implemented in the functional language Haskell and the declarative language Escher. Comparisons are given to other approaches to interaction ..."
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Cited by 111 (3 self)
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How can we integrate interaction into a purely declarative language? This tutorial describes a solution to this problem based on a monad. The solution has been implemented in the functional language Haskell and the declarative language Escher. Comparisons are given to other approaches to interaction based on synchronous streams, continuations, linear logic, and side effects.
Type Classes: An Exploration of the Design Space
 In Haskell Workshop
, 1997
"... When type classes were first introduced in Haskell they were regarded as a fairly experimental language feature, and therefore warranted a fairly conservative design. Since that time, practical experience has convinced many programmers of the benefits and convenience of type classes. However, on occ ..."
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Cited by 106 (8 self)
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When type classes were first introduced in Haskell they were regarded as a fairly experimental language feature, and therefore warranted a fairly conservative design. Since that time, practical experience has convinced many programmers of the benefits and convenience of type classes. However, on occasion, these same programmers have discovered examples where seemingly natural applications for type class overloading are prevented by the restrictions imposed by the Haskell design. It is possible to extend the type class mechanism of Haskell in various ways to overcome these limitations, but such proposals must be designed with great care. For example, several different extensions have been implemented in Gofer. Some of these, particularly the support for multiparameter classes, have proved to be very useful, but interactions between other aspects of the design have resulted in a type system that is both unsound and undecidable. Another illustration is the introduction of constructor cla...
Data Parallel Haskell: a status report
, 2007
"... We describe the design and current status of our effort to implement the programming model of nested data parallelism into the Glasgow Haskell Compiler. We extended the original programmingmodel and its implementation, both of which were first popularised by the NESL language, in terms of expressiv ..."
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Cited by 105 (18 self)
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We describe the design and current status of our effort to implement the programming model of nested data parallelism into the Glasgow Haskell Compiler. We extended the original programmingmodel and its implementation, both of which were first popularised by the NESL language, in terms of expressiveness as well as efficiency. Our current aim is to provide a convenient programming environment for SMP parallelism, and especially multicore architectures. Preliminary benchmarks show that we are, at least for some programs, able to achieve good absolute performance and excellent speedups.
A Concurrent Object Calculus: Reduction and Typing
 HLCL'98 TO APPEAR
, 1998
"... We obtain a new formalism for concurrent objectoriented languages by extending Abadi and Cardelli's imperative object calculus with operators for concurrency from thecalculus and with operators for synchronisation based on mutexes. Our syntax of terms is extremely expressive; in a precise sen ..."
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Cited by 84 (4 self)
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We obtain a new formalism for concurrent objectoriented languages by extending Abadi and Cardelli's imperative object calculus with operators for concurrency from thecalculus and with operators for synchronisation based on mutexes. Our syntax of terms is extremely expressive; in a precise sense it unifies notions of expression, process, store, thread, and configuration. We present a chemicalstyle reduction semantics, and prove it equivalent to a structural operational semantics. We identify a deterministic fragment that is closed under reduction and show that it includes the imperative object calculus. A collection of type systems for objectoriented constructs is at the heart of Abadi and Cardelli's work. We recast one of Abadi and Cardelli's firstorder type systems with object types and subtyping in the setting of our calculus and prove subject reduction. Since our syntax of terms includes both stores and running expressions, we avoid the need to separate store typing from typing of expressions. We translate asynchronous communication channels and the choicefree asynchronouscalculus into our calculus to illustrate its expressiveness; the types of readonly and writeonly channels are supertypes of readwrite channels.
Functional Reactive Programming from First Principles
 In ACM SIGPLAN Conference on Programming Language Design and Implementation
, 2000
"... Functional Reactive Programming, or FRP, is a general framework for programming hybrid systems in a highlevel, declarative manner. The key ideas in FRP are its notions of behaviors and events. Behaviors are timevarying, reactive values, while events are timeordered sequences of discretetime ev ..."
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Cited by 82 (5 self)
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Functional Reactive Programming, or FRP, is a general framework for programming hybrid systems in a highlevel, declarative manner. The key ideas in FRP are its notions of behaviors and events. Behaviors are timevarying, reactive values, while events are timeordered sequences of discretetime event occurrences. FRP is the essence of Fran, a domainspeci c language embedded in Haskell for programming reactive animations, but FRP is now also being used in vision, robotics and other control systems applications. In this paper we explore the formal semantics of FRP and how it relates to an implementation based on streams that represent (and therefore only approximate) continuous behaviors. We show that, in the limit as the sampling interval goes to zero, the implementation is faithful to the formal, continuous semantics, but only when certain constraints on behaviors are observed. We explore the nature of these constraints, which vary amongst the FRP primitives. Our results show both the power and limitations of this approach to language design and implementation. As an example of a limitation, we show that streams are incapable of representing instantaneous predicate events over behaviors. 1.