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252
Notions of Computation and Monads
, 1991
"... The i.calculus is considered a useful mathematical tool in the study of programming languages, since programs can be identified with Iterms. However, if one goes further and uses bnconversion to prove equivalence of programs, then a gross simplification is introduced (programs are identified with ..."
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Cited by 730 (15 self)
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The i.calculus is considered a useful mathematical tool in the study of programming languages, since programs can be identified with Iterms. However, if one goes further and uses bnconversion to prove equivalence of programs, then a gross simplification is introduced (programs are identified with total functions from calues to values) that may jeopardise the applicability of theoretical results, In this paper we introduce calculi. based on a categorical semantics for computations, that provide a correct basis for proving equivalence of programs for a wide range of notions of computation.
A Denotational Semantics of Inheritance and its Correctness
, 1995
"... This paper presents a denotational model of inheritance. The model is based on an intuitive motivation of inheritance as a mechanism for deriving modified versions of recursive definitions. The correctness of the model is demonstrated by proving it equivalent to an operational semantics of inheritan ..."
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Cited by 132 (10 self)
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This paper presents a denotational model of inheritance. The model is based on an intuitive motivation of inheritance as a mechanism for deriving modified versions of recursive definitions. The correctness of the model is demonstrated by proving it equivalent to an operational semantics of inheritance based upon the method lookup algorithm of objectoriented languages.
Unboxed values as first class citizens in a nonstrict functional language
 Proceedings of the 5th ACM conference on Functional programming languages and computer architecture
, 1991
"... The code compiled from a nonstrict functional program usually manipulates heapallocated boxed numbers. Compilers for such languages often go to considerable trouble to optimise operations on boxed numbers into simpler operations on their unboxed forms. These optimisations are usually handled in an ..."
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Cited by 105 (15 self)
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The code compiled from a nonstrict functional program usually manipulates heapallocated boxed numbers. Compilers for such languages often go to considerable trouble to optimise operations on boxed numbers into simpler operations on their unboxed forms. These optimisations are usually handled in an ad hoc manner in the code generator, because earlier phases of the compiler have no way to talk about unboxed values.
We present a new approach, which makes unboxed values into (nearly) firstclass citizens. The language, including its type system, is extended to handle unboxed values. The optimisation of boxing and unboxing operations can now be reinterpreted as a set of correctnesspreserving program transformations. Indeed the particular transformations required are ones which a compiler would want to implement anyway. The compiler becomes both simpler and more modular.
Two other benefits accrue. Firstly, the results of strictness analysis can be exploited within the same uniform transformational framework. Secondly, new algebraic data types with unboxed components can be declared. Values of these types can be manipulated much more efficiently than the corresponding boxed versions.
Both a static and a dynamic semantics are given for the augmented language. The denotational dynamic semantics is notable for its use of unpointed domains.
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 98 (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
Projections for Strictness Analysis
, 1987
"... Contexts have been proposed as a means of performing strictness analysis on nonflat domains. Roughly speaking, a context describes how much a subexpression will be evaluated by the surrounding program. This paper shows how contexts can be represented using the notion of projection from domain theo ..."
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Cited by 96 (4 self)
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Contexts have been proposed as a means of performing strictness analysis on nonflat domains. Roughly speaking, a context describes how much a subexpression will be evaluated by the surrounding program. This paper shows how contexts can be represented using the notion of projection from domain theory. This is clearer than the previous explanation of contexts in terms of continuations. In addition, this paper describes finite domains of contexts over the nonflat list domain. This means that recursive context equations can be solved using standard fixpoint techniques, instead of the algebraic manipulation previously used. Praises of lazy functional languages have been widely sung, and so have some curses. One reason for praise is that laziness supports programming styles that are inconvenient or impossible otherwise [Joh87, Hug84, Wad85a]. One reason for cursing is that laziness hinders efficient implementation. Still, acceptable efficiency for lazy languages is at last being achieved...
Bananas in Space: Extending Fold and Unfold to Exponential Types
, 1995
"... Fold and unfold are general purpose functionals for processing and constructing lists. By using the categorical approach of modelling recursive datatypes as fixed points of functors, these functionals and their algebraic properties were generalised from lists to polynomial (sumofproduct) datatypes ..."
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Cited by 95 (6 self)
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Fold and unfold are general purpose functionals for processing and constructing lists. By using the categorical approach of modelling recursive datatypes as fixed points of functors, these functionals and their algebraic properties were generalised from lists to polynomial (sumofproduct) datatypes. However, the restriction to polynomial datatypes is a serious limitation: it precludes the use of exponentials (functionspaces) , whereas it is central to functional programming that functions are firstclass values, and so exponentials should be able to be used freely in datatype definitions. In this paper we explain how Freyd's work on modelling recursive datatypes as fixed points of difunctors shows how to generalise fold and unfold from polynomial datatypes to those involving exponentials. Knowledge of category theory is not required; we use Gofer throughout as our metalanguage, making extensive use of constructor classes. 1 Introduction During the 1980s, Bird and Meertens [6, 22] d...
Polytypic programming
, 2000
"... ... PolyP extends a functional language (a subset of Haskell) with a construct for defining polytypic functions by induction on the structure of userdefined datatypes. Programs in the extended language are translated to Haskell. PolyLib contains powerful structured recursion operators like catamorp ..."
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Cited by 92 (12 self)
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... PolyP extends a functional language (a subset of Haskell) with a construct for defining polytypic functions by induction on the structure of userdefined datatypes. Programs in the extended language are translated to Haskell. PolyLib contains powerful structured recursion operators like catamorphisms, maps and traversals, as well as polytypic versions of a number of standard functions from functional programming: sum, length, zip, (==), (6), etc. Both the specification of the library and a PolyP implementation are presented.
A Generic Account of ContinuationPassing Styles
 Proceedings of the Twentyfirst Annual ACM Symposium on Principles of Programming Languages
, 1994
"... We unify previous work on the continuationpassing style (CPS) transformations in a generic framework based on Moggi's computational metalanguage. This framework is used to obtain CPS transformations for a variety of evaluation strategies and to characterize the corresponding administrative reducti ..."
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Cited by 87 (34 self)
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We unify previous work on the continuationpassing style (CPS) transformations in a generic framework based on Moggi's computational metalanguage. This framework is used to obtain CPS transformations for a variety of evaluation strategies and to characterize the corresponding administrative reductions and inverse transformations. We establish generic formal connections between operational semantics and equational theories. Formal properties of transformations for specific evaluation orders follow as corollaries. Essentially, we factor transformations through Moggi's computational metalanguage. Mapping terms into the metalanguage captures computational properties (e.g., partiality, strictness) and evaluation order explicitly in both the term and the type structure of the metalanguage. The CPS transformation is then obtained by applying a generic transformation from terms and types in the metalanguage to CPS terms and types, based on a typed term representation of the continuation ...