The linear logic of J.-Y. Girard suggests a new type system for functional languages, one which supports operations that "change the world". Values belonging to a linear type must be used exactly once: like the world, they cannot be duplicated or destroyed. Such values require no reference counting or garbage collection, and safely admit destructive array update. Linear types extend Schmidt's notion of single threading; provide an alternative to Hudak and Bloss' update analysis; and offer a practical complement to Lafont and Holmström's elegant linear languages.

Non-strict evaluation improves the expressive power of functional languages at the expense of an apparent loss of efficiency. In this paper we give examples of this expressive power, taking as an example an interactive functional program and describing the programming techniques depending on non-strict evaluation which improved its design. Implementation methods for non-strict languages have delivered poor performance precisely when such programming techniques have been used. This need not be the case, however, and in the second part of the paper we describe Tim, a method of implementing non-strict languages for which the penalty for using lazy evaluation is very small. 1 Introduction Effort in the functional programming community is today divided into two main activities: making efficient implementations of functional languages and exploiting the expressive power of these languages by writing elegant programs. To a large extent these activities are carried out by separate groups of p...

We present a safe embedding of mutable data structures in functional languages. With safety we mean that confluence and (in some sense) referential transparency are maintained. We develop a static criterion based on abstract interpretation which checks that any side-effect which a function may exert via a destructive update remains invisible. The technique opens up the possibility of designing safe and efficient wide-spectrum languages which combine functional and imperative language constructs.

Denotational semantics is now used widely for the formal definition of programming languages but there is a lack of appropriate tools to support language development. General purpose language implementation systems are oriented to syntax with poor support for semantics. Specialised denotational semantics based systems correspond closely to the formalism but are rendered inflexible for language experimentation by their monolithic multiple stages Exploratory language development with formal definitions is better served by a unitary notation, encompassing syntax and semantics, which is close to but simpler than denotational semantics. Interactive implementation of the notation then facilitates language investigation through the direct execution of a formal definition as an interpreter for the defined language. This thesis presents Navel, a run-time typed, applicative order, pure functional programming language with integrated context free grammar rules. Navel has been used to develop prot...

The objective of this thesis is to explore the connections between abstract interpretation and attribute grammars as frameworks in program analysis. Abstract interpretation is a semantics-based program analysis method. A large class of data flow analysis problems can be expressed as non-standard semantics where the “meaning ” contains information about the runtime behaviour of programs. In an abstract interpretation the analysis is proved correct by relating it to the usual semantics for the language. Attribute grammars provide a method and notation to specify code generation and program analysis directly from the syntax of the programming language. They are especially used for describing compilation of programming languages and very efficient evaluators have been developed for subclasses of attribute grammars. By relating abstract interpretation and attribute grammars we obtain a closer connection between the specification and implementation of abstract interpretations which at the same time facilitates the correctness proofs of interpretations. Implementation and specification of abstract interpretations using circular attribute grammars is realised with an evaluator system for a class of domain theoretic attribute grammars. In this system thecircularity of attribute grammars is resolved by fixpoint iteration. The use of finite lattices in abstract interpretations requires automatic generation of specialised fixpoint iterators. This is done using a technique called lazy fixpoint iteration which is presented in the thesis. Methods from abstract interpretation can also be used in correctness proofs of attribute grammars. This proof technique introduces a new class of attribute grammars based on domain theory. This method is illustrated with examples. i ii SUMMARY