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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 111 (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
Simple Relational Correctness Proofs for Static Analyses and Program Transformations
, 2004
"... We show how some classical static analyses for imperative programs, and the optimizing transformations which they enable, may be expressed and proved correct using elementary logical and denotational techniques. The key ingredients are an interpretation of program properties as relations, rather tha ..."
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Cited by 104 (9 self)
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We show how some classical static analyses for imperative programs, and the optimizing transformations which they enable, may be expressed and proved correct using elementary logical and denotational techniques. The key ingredients are an interpretation of program properties as relations, rather than predicates, and a realization that although many program analyses are traditionally formulated in very intensional terms, the associated transformations are actually enabled by more liberal extensional properties.
Monads and Effects
 IN INTERNATIONAL SUMMER SCHOOL ON APPLIED SEMANTICS APPSEM’2000
, 2000
"... A tension in language design has been between simple semantics on the one hand, and rich possibilities for sideeffects, exception handling and so on on the other. The introduction of monads has made a large step towards reconciling these alternatives. First proposed by Moggi as a way of structu ..."
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Cited by 68 (6 self)
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A tension in language design has been between simple semantics on the one hand, and rich possibilities for sideeffects, exception handling and so on on the other. The introduction of monads has made a large step towards reconciling these alternatives. First proposed by Moggi as a way of structuring semantic descriptions, they were adopted by Wadler to structure Haskell programs, and now offer a general technique for delimiting the scope of effects, thus reconciling referential transparency and imperative operations within one programming language. Monads have been used to solve longstanding problems such as adding pointers and assignment, interlanguage working, and exception handling to Haskell, without compromising its purely functional semantics. The course will introduce monads, effects and related notions, and exemplify their applications in programming (Haskell) and in compilation (MLj). The course will present typed metalanguages for monads and related categorica...
Relational reasoning in a nominal semantics for storage
 In Proc. 7th International Conference on Typed Lambda Calculi and Applications (TLCA), volume 3461 of Lecture Notes in Computer Science
, 2005
"... a higherorder CBV language with recursion and dynamically allocated mutable references that may store both ground data and the addresses of other references, but not functions. This model is adequate, though far from fully abstract. We then develop a relational reasoning principle over the denotati ..."
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Cited by 66 (13 self)
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a higherorder CBV language with recursion and dynamically allocated mutable references that may store both ground data and the addresses of other references, but not functions. This model is adequate, though far from fully abstract. We then develop a relational reasoning principle over the denotational model, and show how it may be used to establish various contextual equivalences involving allocation and encapsulation of store. 1
Operational Semantics and Program Equivalence
 INRIA Sophia Antipolis, 2000. Lectures at the International Summer School On Applied Semantics, APPSEM 2000, Caminha, Minho
, 2000
"... This tutorial paper discusses a particular style of operational semantics that enables one to give a `syntaxdirected' inductive definition of termination which is very useful for reasoning about operational equivalence of programs. We restrict attention to contextual equivalence of express ..."
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Cited by 41 (4 self)
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This tutorial paper discusses a particular style of operational semantics that enables one to give a `syntaxdirected' inductive definition of termination which is very useful for reasoning about operational equivalence of programs. We restrict attention to contextual equivalence of expressions in the ML family of programming languages, concentrating on functions involving local state. A brief tour of structural operational semantics culminates in a structural definition of termination via an abstract machine using `frame stacks'. Applications of this to reasoning about contextual equivalence are given.
A Definitional Approach to Primitive Recursion over Higher Order Abstract Syntax
 In Proceedings of the 2003 workshop on Mechanized
, 2003
"... Syntax S. J. Ambler (S.Ambler@mcs.le.ac.uk) R. L. Crole (R.Crole@mcs.le.ac.uk) & A. Momigliano (A.Momigliano@mcs.le.ac.uk) Department of Mathematics and Computer Science, University of Leicester, Leicester, LE1 7RH, U.K. ..."
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Cited by 27 (5 self)
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Syntax S. J. Ambler (S.Ambler@mcs.le.ac.uk) R. L. Crole (R.Crole@mcs.le.ac.uk) & A. Momigliano (A.Momigliano@mcs.le.ac.uk) Department of Mathematics and Computer Science, University of Leicester, Leicester, LE1 7RH, U.K.
A Definitional TwoLevel Approach to Reasoning with HigherOrder Abstract Syntax
 Journal of Automated Reasoning
, 2010
"... Abstract. Combining higherorder abstract syntax and (co)induction in a logical framework is well known to be problematic. Previous work [ACM02] described the implementation of a tool called Hybrid, within Isabelle HOL, syntax, and reasoned about using tactical theorem proving and principles of (co ..."
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Abstract. Combining higherorder abstract syntax and (co)induction in a logical framework is well known to be problematic. Previous work [ACM02] described the implementation of a tool called Hybrid, within Isabelle HOL, syntax, and reasoned about using tactical theorem proving and principles of (co)induction. Moreover, it is definitional, which guarantees consistency within a classical type theory. The idea is to have a de Bruijn representation of syntax, while offering tools for reasoning about them at the higher level. In this paper we describe how to use it in a multilevel reasoning fashion, similar in spirit to other metalogics such as Linc and Twelf. By explicitly referencing provability in a middle layer called a specification logic, we solve the problem of reasoning by (co)induction in the presence of nonstratifiable hypothetical judgments, which allow very elegant and succinct specifications of object logic inference rules. We first demonstrate the method on a simple example, formally proving type soundness (subject reduction) for a fragment of a pure functional language, using a minimal intuitionistic logic as the specification logic. We then prove an analogous result for a continuationmachine presentation of the operational semantics of the same language, encoded this time in an ordered linear logic that serves as the specification layer. This example demonstrates the ease with which we can incorporate new specification logics, and also illustrates a significantly
A Monadic Multistage Metalanguage
, 2003
"... We describe a metalanguage MMML, which makes explicit the order of evaluation (in the spirit of monadic metalanguages) and the staging of computations (as in languages for multilevel bindingtime analysis). The main contribution of the paper is an operational semantics which is sufficiently detaile ..."
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Cited by 17 (7 self)
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We describe a metalanguage MMML, which makes explicit the order of evaluation (in the spirit of monadic metalanguages) and the staging of computations (as in languages for multilevel bindingtime analysis). The main contribution of the paper is an operational semantics which is sufficiently detailed for analyzing subtle aspects of multistage programming, but also intuitive enough to serve as a reference semantics. For instance, the separation of computational types from code types, makes clear the distinction between a computation for generating code and the generated code, and provides a basis for multilingual extensions, where a variety of programming languages (aka monads) coexist. The operational semantics consists of two parts: local (semantics preserving) simplification rules, and computation steps executed in a deterministic order (because they may have sideeffects). We focus on the computational aspects, thus we adopt a simple type system, that can detect usual type errors, but not the unresolved link errors. Because of its explicit annotations, MMML is suitable as an intermediate language.
Semantics of an effect analysis for exceptions
 In Proc. of TLDI 2007
, 2007
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Algebraic foundations for effectdependent optimisations
 In POPL
, 2012
"... We present a general theory of Giffordstyle type and effect annotations, where effect annotations are sets of effects. Generality is achieved by recourse to the theory of algebraic effects, a development of Moggi’s monadic theory of computational effects that emphasises the operations causing the e ..."
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Cited by 14 (1 self)
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We present a general theory of Giffordstyle type and effect annotations, where effect annotations are sets of effects. Generality is achieved by recourse to the theory of algebraic effects, a development of Moggi’s monadic theory of computational effects that emphasises the operations causing the effects at hand and their equational theory. The key observation is that annotation effects can be identified with operation symbols. We develop an annotated version of Levy’s CallbyPushValue language with a kind of computations for every effect set; it can be thought of as a sequential, annotated intermediate language. We develop a range of validated optimisations (i.e., equivalences), generalising many existing ones and adding new ones. We classify these optimisations as structural, algebraic, or abstract: structural optimisations always hold; algebraic ones depend on the effect theory at hand; and abstract ones depend on the global nature of that theory (we give modularlycheckable sufficient conditions for their validity).