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Between Functions and Relations in Calculating Programs
, 1992
"... This thesis is about the calculational approach to programming, in which one derives programs from specifications. One such calculational paradigm is Ruby, the relational calculus developed by Jones and Sheeran for describing and designing circuits. We identify two shortcomings with derivations made ..."
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Cited by 15 (4 self)
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This thesis is about the calculational approach to programming, in which one derives programs from specifications. One such calculational paradigm is Ruby, the relational calculus developed by Jones and Sheeran for describing and designing circuits. We identify two shortcomings with derivations made using Ruby. The first is that the notion of a program being an implementation of a specification has never been made precise. The second is to do with types. Fundamental to the use of type information in deriving programs is the idea of having types as special kinds of programs. In Ruby, types are partial equivalence relations (pers). Unfortunately, manipulating some formulae involving types has proved difficult within Ruby. In particular, the preconditions of the `induction' laws that are much used within program derivation often work out to be assertions about types; such assertions have typically been verified either by informal arguments or by using predicate calculus, rather than by ap...
Making Functionality More General
 In Functional Programming, Glasgow 1991, Workshops in computing
, 1992
"... The notion of functionality is not cast in stone, but depends upon what we have as types in our language. With partial equivalence relations (pers) as types we show that the functional relations are precisely those satisfying the simple equation f = f ffi f [ ffi f , where " [ " is th ..."
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Cited by 7 (1 self)
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The notion of functionality is not cast in stone, but depends upon what we have as types in our language. With partial equivalence relations (pers) as types we show that the functional relations are precisely those satisfying the simple equation f = f ffi f [ ffi f , where " [ " is the relation converse operator. This article forms part of "A calculational theory of pers as types" [1]. 1 Introduction In calculational programming, programs are derived from specifications by a process of algebraic manipulation. Perhaps the best known calculational paradigm is the BirdMeertens formalism, or to use its more colloquial name, Squiggol [2]. Programs in the Squiggol style work upon trees, lists, bags and sets, the socalled Boom hierarchy. The framework was uniformly extended to cover arbitrary recursive types by Malcolm in [3], by means of the Falgebra paradigm of type definition, and resulting catamorphic programming style. More recently, Backhouse et al [4] have made a further ...
Back to Basics: Deriving Representations Changers Without Relations
, 1994
"... A representation changer is a function that can be specified in a particular way in terms of two other functions. Examples of representation changers include binary addition and multiplication, base conversion, and compilers. There has been much recent work in using a relational language, namely ..."
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Cited by 6 (0 self)
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A representation changer is a function that can be specified in a particular way in terms of two other functions. Examples of representation changers include binary addition and multiplication, base conversion, and compilers. There has been much recent work in using a relational language, namely Jones and Sheerans' Ruby, to derive representation changers from their specifications using equational reasoning. In this paper
A Calculational Theory of Pers as Types
, 1992
"... We present a programming paradigm based upon the notion of binary relations as programs, and partial equivalence relations (pers) as types. Our method is calculational , in that programs are derived from specifications by algebraic manipulation. Working with relations as programs generalises the fu ..."
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Cited by 5 (2 self)
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We present a programming paradigm based upon the notion of binary relations as programs, and partial equivalence relations (pers) as types. Our method is calculational , in that programs are derived from specifications by algebraic manipulation. Working with relations as programs generalises the functional paradigm, admiting nondeterminism and the use of relation converse. Working with pers as types, we have a more general notion than normal of what constitutes an element of a type; this leads to a more general class of functional relations, the socalled difunctional relations. Our basic method of defining types is to take the fixpoint of a relator , a simple strengthening of the categorical notion of a functor. Further new types can be made by imposing laws and restrictions on the constructors of other types. Having pers as types is fundamental to our treatment of types with laws. Contents 1 Introduction 2 2 Relational calculus 4 2.1 Powerset lattice structure : : : : : : : : :...
Invariant Assertions, Invariant Relations, and Invariant Functions
, 2012
"... Invariant assertions play an important role in the analysis and documentation of while loops of imperative programs. Invariant functions and invariant relations are alternative analysis tools that are distinct from invariant assertions but are related to them. In this paper we discuss these three co ..."
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Invariant assertions play an important role in the analysis and documentation of while loops of imperative programs. Invariant functions and invariant relations are alternative analysis tools that are distinct from invariant assertions but are related to them. In this paper we discuss these three concepts and analyze their relationships. The study of invariant functions and invariant relations is interesting not only because it provides alternative means to analyze loops, but also because it gives us insights into the structure of invariant assertions, hence may help us enhance techniques for generating invariant assertions.
Making functionality more general
, 1992
"... Abstract The notion of functionality is not cast in stone, but depends upon what we have as types in our language. With partial equivalence relations (pers) as types we show that the functional relations are precisely those satisfying the simple equation f = f ffi f [ ffi f, where "[ &q ..."
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Abstract The notion of functionality is not cast in stone, but depends upon what we have as types in our language. With partial equivalence relations (pers) as types we show that the functional relations are precisely those satisfying the simple equation f = f ffi f [ ffi f, where &quot;[ &quot; is the relation converse operator. This article forms part of &quot;A calculational theory of pers as types &quot; [1].