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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 278 (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.
An OpenEnded Finite Domain Constraint Solver
, 1997
"... We describe the design and implementation of a finite domain constraint solver embedded in a Prolog system using an extended unification mechanism via attributed variables as a generic constraint interface. The solver is essentially a scheduler for indexicals, i.e. reactive functional rules encodin ..."
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Cited by 186 (8 self)
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We describe the design and implementation of a finite domain constraint solver embedded in a Prolog system using an extended unification mechanism via attributed variables as a generic constraint interface. The solver is essentially a scheduler for indexicals, i.e. reactive functional rules encoding local consistency methods performing incremental constraint solving or entailment checking, and global constraints, i.e. general propagators which may use specialized algorithms to achieve a higher degree of consistency or better time and space complexity. The solver has an openended design: the user can introduce new constraints, either in terms of indexicals by writing rules in a functional notation, or as global constraints via a Prolog programming interface. Constraints defined in terms of indexicals can be linked to 0/1variables modeling entailment; thus indexicals are used for constraint solving as well as for entailment testing. Constraints can be arbitrarily combined using the ...
A Survey of Automated Timetabling
, 1999
"... The timetabling problem consists in scheduling a sequence of lectures between teachers and students in a prefixed period of time (typically a week), satisfying a set of constraints of various types. A large number of variants of the timetabling problem have been proposed in the literature, which d ..."
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Cited by 179 (14 self)
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The timetabling problem consists in scheduling a sequence of lectures between teachers and students in a prefixed period of time (typically a week), satisfying a set of constraints of various types. A large number of variants of the timetabling problem have been proposed in the literature, which differ from each other based on the type of institution involved (university or school) and the type of constraints. This problem, that has been traditionally considered in the operational research field, has recently been tackled with techniques belonging also to Artificial Intelligence (e.g., genetic algorithms, tabu search, and constraint satisfaction). In this paper, we survey the various formulations of the problem, and the techniques and algorithms used for its solution.
A unified computation model for functional and logic programming
 IN PROC. OF THE 24TH ACM SYMPOSIUM ON PRINCIPLES OF PROGRAMMING LANGUAGES (PARIS
, 1997
"... We propose a new computation model which combines the operational principles of functional languages (reduction), logic languages (nondeterministic search for solutions), and integrated functional logic languages (residuation and narrowing). This computation model combines efficient evaluation prin ..."
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Cited by 142 (69 self)
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We propose a new computation model which combines the operational principles of functional languages (reduction), logic languages (nondeterministic search for solutions), and integrated functional logic languages (residuation and narrowing). This computation model combines efficient evaluation principles of functional languages with the problemsolving capabilities of logic programming. Since the model allows the delay of function calls which are not sufficiently instantiated, it also supports a concurrent style of programming. We provide soundness and completeness results and show that known evaluation principles of functional logic languages are particular instances of this model. Thus, our model is a suitable basis for future declarative programming languages.
An Asynchronous Model of Locality, Failure, and Process Mobility
 Theoretical Computer Science
, 1997
"... We present a model of distributed computation which is based on a fragment of the picalculus relying on asynchronous communication. We enrich the model with the following features: the explicit distribution of processes to locations, the failure of locations and their detection, and the mobility of ..."
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Cited by 119 (4 self)
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We present a model of distributed computation which is based on a fragment of the picalculus relying on asynchronous communication. We enrich the model with the following features: the explicit distribution of processes to locations, the failure of locations and their detection, and the mobility of processes. Our contributions are two folds. At the specification level, we give a synthetic and flexible formalization of the features mentioned above. At the verification level, we provide original methods to reason about the bisimilarity of processes in the presence of failures.
Excluding Symmetries in ConstraintBased Search
, 1999
"... . We introduce a new method for excluding symmetries in constraint based search. To our knowledge, it is the rst declarative method that can be applied to arbitrary symmetries. Our method is based on the notion of symmetric constraints, which are used in our modication of a general constraint ba ..."
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Cited by 86 (5 self)
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. We introduce a new method for excluding symmetries in constraint based search. To our knowledge, it is the rst declarative method that can be applied to arbitrary symmetries. Our method is based on the notion of symmetric constraints, which are used in our modication of a general constraint based search algorithm. The method does not inuence the search strategy. Furthermore, it can be used with either the full set of symmetries, or with an subset of all symmetries. We proof correctness, completeness and symmetry exclusion properties of our method. We then show how to apply the method in the special case of geometric symmetries (rotations and reections) and permutation symmetries. Furthermore, we give results from practical applications. 1 Introduction In many search problems, one is faced with the existence of symmetries. Symmetries give rise to many dierent solutions found by the search procedure, which are all considered to be "similar". Often, one is not intereste...
Compiling MultiParadigm Declarative Programs into Prolog
 In Proc. International Workshop on Frontiers of Combining Systems (FroCoS’2000
, 2000
"... This paper describes a highlevel implementation of the concurrent constraint functional logic language Curry. The implementation, directed by the lazy pattern matching strategy of Curry, is obtained by transforming Curry programs into Prolog programs. Contrary to previous transformations of functio ..."
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Cited by 57 (37 self)
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This paper describes a highlevel implementation of the concurrent constraint functional logic language Curry. The implementation, directed by the lazy pattern matching strategy of Curry, is obtained by transforming Curry programs into Prolog programs. Contrary to previous transformations of functional logic programs into Prolog, our implementation includes new mechanisms for both efficiently performing concurrent evaluation steps and sharing common subterms. The practical results show that our implementation is superior to previously proposed similar implementations of functional logic languages in Prolog and is competitive w.r.t. lowerlevel implementations of Curry in other target languages. An noteworthy advantage of our implementation is the ability to immediately employ in Curry existing constraint solvers for logic programming. In this way, we obtain with a relatively modest effort the implementation of a declarative language combining lazy evaluation, concurrency a...
Curry: A Truly Functional Logic Language
, 1995
"... Functional and logic programming are the most important declarative programming paradigms, and interest in combining them has grown over the last decade. However, integrated functional logic languages are currently not widely used. This is due to the fact that the operational principles are not w ..."
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Cited by 54 (5 self)
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Functional and logic programming are the most important declarative programming paradigms, and interest in combining them has grown over the last decade. However, integrated functional logic languages are currently not widely used. This is due to the fact that the operational principles are not well understood and many different evaluation strategies have been proposed which resulted in many different functional logic languages. To overcome this situation, we propose the functional logic language Curry which can deal as a standard language in this area. It includes important ideas of existing functional logic languages and recent developments, and combines the most important features of functional and logic languages. Thus, Curry can be the basis to combine the currently separated research efforts of the functional and logic programming communities and to boost declarative programming in general. Moreover, since functions provide for more efficient evaluation strategies and ...
Oz Explorer: A Visual Constraint Programming Tool
, 1997
"... This paper describes the Oz Explorer and its implementation. The Explorer is a visual constraint programming tool intended to support the development of constraint programs. It uses the search tree of a constraint problem as its central metaphor. Exploration and visualization of the search tree ar ..."
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Cited by 54 (1 self)
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This paper describes the Oz Explorer and its implementation. The Explorer is a visual constraint programming tool intended to support the development of constraint programs. It uses the search tree of a constraint problem as its central metaphor. Exploration and visualization of the search tree are userdriven and interactive. The constraints of any node in the tree are available firstclass: predefined or userdefined procedures can be used to display or analyze them. The Explorer is a fast and memory efficient tool intended for the development of realworld constraint programs. The Explorer is implemented in Oz using firstclass computation spaces. There is no fixed search strategy in Oz. Instead, firstclass computation spaces allow to program search engines. The Explorer is one particular example of a userguided search engine. The use of recomputation to trade space for time makes it possible to solve large realworld problems, which would use too much memory otherwise.