The type and effect discipline is a new framework for reconstructing the principal type and the minimal effect of expressions in implicitly typed polymorphic functional languages that support imperative constructs. The type and effect discipline outperforms other polymorphic type systems. Just as types abstract collections of concrete values, effects denote imperative operations on regions. Regions abstract sets of possibly aliased memory locations. Effects are used to control type generalization in the presence of imperative constructs while regions delimit observable side-effects. The observable effects of an expression range over the regions that are free in its type environment and its type; effects related to local data structures can be discarded during type reconstruction. The type of an expression can be generalized with respect to the variables that are not free in the type environment or in the observable effect. 1 Introduction Type inference [12] is the process that automa...

We describe a system that supports source-level integration of ML-like functional language code with ANSI C or Ada83 code. The system works by translating the functional code into type-correct, "vanilla" C or Ada; it offers simple, efficient, type-safe inter-operation between new functional code components and "legacy" third-generationlanguage components. Our translator represents a novel synthesis of techniques including user-parameterized specification of primitive types and operators; removal of polymorphism by code specialization; removal of higher-order functions using closure datatypes and interpretation; and aggressive optimization of the resulting first-order code, which can be viewed as encoding the result of a closure analysis. Programs remain fully typed at every stage of the translation process, using only simple, standard type systems. Target code runs at speeds comparable to the output of current optimizing ML compilers, even though handicapped by a conservative garbage collector.

We describe a type system and typed semantics that use a hierarchy of monads to describe and delimit a variety of effects, including non-termination, exceptions, and state, in a call-by-value functional language. The type system and semantics can be used to organize and justify avariety of optimizing transformations in the presence of effects. In addition, we describe a simple monad inferencing algorithm that computes the minimum effect for each subexpression of a program, and provides more accurate effects information than local syntactic methods.

The familiar Hindley-Milner type system of the ML language family is extended with monad annotations to account for possible side effects of expression evaluation. This also allows effects to be effectively encapsulated by lexical scopes, with enforcement provided by type checking. A type-and-effects analysis supports type inference. Type soundness and completeness theorems establish the coherence of monadic type inference with the reference semantics of a small ML-style language. 1 Introduction Modern functional languages such as Haskell, Standard ML, CAML and Clean have evolved into wide spectrum programming languages through the addition of imperative features and foreign-language interfaces to a purely functional core. This evolution has been necessary to make these languages practical vehicles for the design and implementation of software systems but it has impaired our ability to reason about and formally manipulate programs. When evaluation of an expression may produce a side ...

Effect systems extend classical type systems with effect information. Just as types describe the possible values of expressions, effects describe their possible evaluation behaviors. Effects, which appear in function types, introduce new constraints on the typability of expressions. To increase the exibility and accuracy of e ect systems, we present a new effect system based on subtyping. The subtype relation is induced by a subsumption relation on effects. This subtyping effect system avoids merging effect information together, thus collecting more precise effect information. We introduce a reconstruction algorithm which for any expression already typed with classical types, reconstructs its type and effect based on the subtype relation. The reconstruction algorithm is sound and complete w.r.t. the static semantics.

iii Acknowledgements vi 1

We havedesigned and implemented an asynchronous data-parallel scheduler for the SML/NJ ML compiler. Using this general scheduler we built a data-parallel module that provides new operators to manipulate sequences (i.e., arrays, vectors) in parallel. Parallelization concerns such as thread creation and synchronization are hidden from the application programmer by ML's module abstraction. We nd that languages with modules, higher-order functions and automatic parallel storage management can, in this manner, seamlessly support data-parallel operators. An implementation of applications using the new sequence module on an eight-processor shared-memory machine indicates that in some cases useful speedup is possible with our approach. 1

pour obtenir le dipl^ome d'Habilitation a Diriger des Recherches en Sciences de l'Universite de Paris XI. Pour completement apprecier le contenu de ces recherches, le lecteur pourra se reporter avec pro t au texte complet des articles donnes en annexe. 1 Remerciements L'ensemble de ces travaux n'aurait pu ^etre ce qu'il est sans le concours de nombreux chercheurs et amis qu'il m'est un plaisir de remercier ici: Au Centre de Recherche en Informatique (CRI) de l'Ecole des Mines de Paris, mon colocataire