Results 1 
9 of
9
Putting Type Annotations to Work
, 1996
"... We study an extension of the HindleyMilner system with explicit type scheme annotations and type declarations. The system can express polymorphic function arguments, userdefined data types with abstract components, and structure types with polymorphic fields. More generally, all programs of the po ..."
Abstract

Cited by 96 (1 self)
 Add to MetaCart
We study an extension of the HindleyMilner system with explicit type scheme annotations and type declarations. The system can express polymorphic function arguments, userdefined data types with abstract components, and structure types with polymorphic fields. More generally, all programs of the polymorphic lambda calculus can be encoded by a translation between typing derivations. We show that type reconstruction in this system can be reduced to the decidable problem of firstorder unification under a mixed prefix.
On perfect supercompilation
 Journal of Functional Programming
, 1996
"... We extend positive supercompilation to handle negative as well as positive information. This is done by instrumenting the underlying unfold rules with a small rewrite system that handles constraints on terms, thereby ensuring perfect information propagation. We illustrate this by transforming a na ..."
Abstract

Cited by 80 (3 self)
 Add to MetaCart
We extend positive supercompilation to handle negative as well as positive information. This is done by instrumenting the underlying unfold rules with a small rewrite system that handles constraints on terms, thereby ensuring perfect information propagation. We illustrate this by transforming a naively specialised string matcher into an optimal one. The presented algorithm is guaranteed to terminate by means of generalisation steps.
Practical ModelBased Static Analysis for Definite Logic Programs
, 1995
"... The declarative semantics of definite logic programs is the basis of an elegant and practical framework for their static analysis. We define a core semantics parameterised by a preinterpretation of the language underlying the program. The concrete semantics is given by an extended Herbrand interpret ..."
Abstract

Cited by 28 (13 self)
 Add to MetaCart
The declarative semantics of definite logic programs is the basis of an elegant and practical framework for their static analysis. We define a core semantics parameterised by a preinterpretation of the language underlying the program. The concrete semantics is given by an extended Herbrand interpretation, capturing the correct answers of a program. The semantics is computed as the least fixed point of an immediate consequences operator. An abstract semantics is specified simply by giving, for each constant and function in the program, a denotation in an abstract domain of interpretation. No abstract operations such as abstract unification need to be defined. The directness and simplicity of this approach is then illustrated by specifying and implementing a number of abstract interpretations. These include various mode analyses, analyses on the structure of lists and the length of lists, and simple and polymorphic types. The implementations used for the experiments are based on abstract...
Rank 2 Type Systems and Recursive Definitions
, 1995
"... We demonstrate an equivalence between the rank 2 fragments of the polymorphic lambda calculus (System F) and the intersection type discipline: exactly the same terms are typable in each system. An immediate consequence is that typability in the rank 2 intersection system is DEXPTIMEcomplete. We int ..."
Abstract

Cited by 26 (1 self)
 Add to MetaCart
We demonstrate an equivalence between the rank 2 fragments of the polymorphic lambda calculus (System F) and the intersection type discipline: exactly the same terms are typable in each system. An immediate consequence is that typability in the rank 2 intersection system is DEXPTIMEcomplete. We introduce a rank 2 system combining intersections and polymorphism, and prove that it types exactly the same terms as the other rank 2 systems. The combined system suggests a new rule for typing recursive definitions. The result is a rank 2 type system with decidable type inference that can type some interesting examples of polymorphic recursion. Finally,we discuss some applications of the type system in data representation optimizations such as unboxing and overloading.
Formal Verification of Algorithm W: The Monomorphic Case
, 1996
"... A formal verification of the soundness and completeness of Milner's type inference algorithm W for simply typed lambdaterms is presented. Particular attention is paid to the notorious issue of "new" variables. The proofs are carried out in Isabelle/HOL, the HOL instantiation of t ..."
Abstract

Cited by 10 (1 self)
 Add to MetaCart
A formal verification of the soundness and completeness of Milner's type inference algorithm W for simply typed lambdaterms is presented. Particular attention is paid to the notorious issue of "new" variables. The proofs are carried out in Isabelle/HOL, the HOL instantiation of the generic theorem prover Isabelle.
On the Design of a Correct Freeness Analysis for Logic Programs
, 1996
"... Several proposals for computing freeness information for logic programs have been put forward in recent literature. The availability of such information has proven useful in a variety of applications, including parallelization of Prolog programs, optimizations in Prolog compilers, as well as for imp ..."
Abstract

Cited by 8 (1 self)
 Add to MetaCart
Several proposals for computing freeness information for logic programs have been put forward in recent literature. The availability of such information has proven useful in a variety of applications, including parallelization of Prolog programs, optimizations in Prolog compilers, as well as for improving the precision of other analyses. While these proposals have illustrated the importance of such analyses, they lack formal justification. Moreover, several have been found incorrect. This paper introduces a novel domain of abstract equation systems describing possible sharing and definite freeness of terms in a system of equations. A simple and intuitive abstract unification algorithm is presented, providing the core of a correct and precise sharing and freeness analysis for logic programs. Our contribution is not only a correct algorithm, but perhaps primarily, the application of a systematic approach in which it is derived by mimicking each step in a suitable concrete unification al...
On Transformations into Linear Database Logic Programs
 Perspectives of Systems Informatics, 2nd International Andrei Ershov Memorial Conference, Akademgorodik
, 1996
"... Abstract. We consider the problem of transformations of logic programs without function symbols (database logic programs) into a special subclass, namely linear logic programs. Linear logic programs are dened to be the programs whose rules have at most one intentional atom in their bodies. a) We inv ..."
Abstract

Cited by 6 (5 self)
 Add to MetaCart
Abstract. We consider the problem of transformations of logic programs without function symbols (database logic programs) into a special subclass, namely linear logic programs. Linear logic programs are dened to be the programs whose rules have at most one intentional atom in their bodies. a) We investigate linearizability of several syntactically de ned subclasses of programs and present both positive and negative results (i.e. demonstrate programs that cannot be transformed into a linear program by any transformation technique), and b) We develop an algorithm which transforms any program in a speci c subclass namely the piecewise logic programs into a linear logic program.
Linearisability on Datalog Programs?
"... Linear Datalog programs are programs whose clauses haveatmostoneintensional atom in their bodies. We explore syntactic classes of Datalog programs (syntactically nonlinear) which turn out to express no more than the queries expressed by linear Datalog programs. In particular, we investigate lineari ..."
Abstract
 Add to MetaCart
Linear Datalog programs are programs whose clauses haveatmostoneintensional atom in their bodies. We explore syntactic classes of Datalog programs (syntactically nonlinear) which turn out to express no more than the queries expressed by linear Datalog programs. In particular, we investigate linearisability of (database queries corresponding to) piecewise linear Datalog programs and chain queries: a) We prove that piecewise linear Datalog programs can always be transformed into linear Datalog programs, by virtue of a procedure which performs the transformation automatically. The procedure relies upon conventional logic program transformation techniques. b) We identify a new class of linearisable chain queries, referred to as pseudoregular, and prove their linearisability constructively, by generating, for any given pseudoregular chain query, the Datalog program corresponding to it.