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...

Achieving good performance in bytecoded language interpreters is difficult without sacrificing both simplicity and portability. This is due to the complexity of dynamic translation ("just-in-time compilation") of bytecodes into native code, which is the mechanism employed universally by highperformance interpreters. We demonstrate that a few simple techniques make it possible to create highly-portable dynamic translators that can attain as much as 70% the performance of optimized C for certain numerical computations. Translators based on such techniques can offer respectable performance without sacrificing either the simplicity or portability of much slower "pure" bytecode interpreters. Keywords: bytecode interpretation, threaded code, inlining, dynamic translation, just-in-time compilation. 1 Introduction Bytecoded languages such as Smalltalk [Gol83], Caml [Ler97] and Java [Arn96, Lin97] offer significant engineering advantages over more conventional languages: higher levels of abst...

. The SML-like module systems are small typed languages of their own. As is, one would expect a proof of their soundness following from a proof of subject reduction. Unfortunately, the subject-reduction property and the preservation of type abstraction seem to be incompatible. As a consequence, in relevant module systems, the theoretical study of reductions is meaningless, and for instance, the question of normalization of module expressions can not even be considered. In this paper, we analyze this problem as a misunderstanding of the notion of module definition. We build a variant of the SML module system --- inspired from recent works by Leroy, Harper, and Lillibridge --- which enjoys the subject reduction property. Type abstraction --- achieved through an explicit declaration of the signature of a module at its definition --- is preserved. This was the initial motivation. Besides our system enjoys other type-theoretic properties: the calculus is strongly normalizing, there are no syntactic restrictions on module paths, it enjoys a purely applicative semantics and type inference is decidable. Neither Leroy's system nor Harper and Lillibridge's system has all of them.

Abstract. Sledgehammer for Isabelle/HOL integrates automatic theorem provers to discharge interactive proof obligations. This paper considers a tighter integration of the superposition prover SPASS to increase Sledgehammer’s success rate. The main enhancements are native support for hard sorts (simple types) in SPASS, simplification that honors the orientation of Isabelle simp rules, and a pair of clause-selection strategies targeted at large lemma libraries. The usefulness of this integration is confirmed by an evaluation on a vast benchmark suite and by a case study featuring a formalization of language-based security. 1

The theoretical study of micron-scale quantum-mechanical systems generally begins with two assumptions about the potential: that there is no background potential, and that any confining potential is hard-walled. In this thesis, we will look at a phenomenon that is seen when these assumptions are not made, in the context of electron conductance through two-dimensional electron gasses (2DEGs).