Space-Efficient Gradual Typing in Coercion-Passing Style

Herman et al. pointed out that the insertion of run-time checks into a gradually typed program could hamper tail-call optimization and, as a result, worsen the space complexity of the program. To address the problem, they proposed a space-efficient coercion calculus, which was subsequently improved by Siek et al. The semantics of these calculi involves eager composition of run-time checks expressed by coercions to prevent the size of a term from growing. However, it relies also on a nonstandard reduction rule, which does not seem easy to implement. In fact, no compiler implementation of gradually typed languages fully supports the space-efficient semantics faithfully. In this paper, we study coercion-passing style, which Herman et al. have already mentioned, as a technique for straightforward space-efficient implementation of gradually typed languages. A program in coercion-passing style passes "the rest of the run-time checks" around - just like continuation-passing style (CPS), in which "the rest of the computation" is passed around - and (unlike CPS) composes coercions eagerly. We give a formal coercion-passing translation from ?S by Siek et al. to ?S?, which is a new calculus of first-class coercions tailored for coercion-passing style, and prove correctness of the translation. We also implement our coercion-passing style transformation for the Grift compiler developed by Kuhlenschmidt et al. An experimental result shows stack overflow can be prevented properly at the cost of up to 3 times slower execution for most partially typed practical programs

Gradual Liquid Type Inference

Liquid typing provides a decidable refinement inference mechanism that is convenient but subject to two major issues: (1) inference is global and requires top-level annotations, making it unsuitable for inference of modular code components and prohibiting its applicability to library code, and (2) inference failure results in obscure error messages. These difficulties seriously hamper the migration of existing code to use refinements. This paper shows that gradual liquid type inference---a novel combination of liquid inference and gradual refinement types---addresses both issues. Gradual refinement types, which support imprecise predicates that are optimistically interpreted, can be used in argument positions to constrain liquid inference so that the global inference process e effectively infers modular specifications usable for library components. Dually, when gradual refinements appear as the result of inference, they signal an inconsistency in the use of static refinements. Because liquid refinements are drawn from a nite set of predicates, in gradual liquid type inference we can enumerate the safe concretizations of each imprecise refinement, i.e. the static refinements that justify why a program is gradually well-typed. This enumeration is useful for static liquid type error explanation, since the safe concretizations exhibit all the potential inconsistencies that lead to static type errors. We develop the theory of gradual liquid type inference and explore its pragmatics in the setting of Liquid Haskell.Comment: To appear at OOPSLA 201

Complementarity constraints and induced innovation: Some evidence from the first IT regime

Technological search is often depicted to be random. This paper takes a different view and analyses how innovative recombinant search is triggered, how it is done and what initial conditions influence the final design of technological artefacts. We argue that complementarities (non-separabilities) play an important role as focusing devices guiding the search for new combinations. Our analysis takes the perspective of technology adopters and not that of inventors or innovators of new products. We illustrate the process of decomposition and re-composition under the presence of binding complementarity constraints with a historical case study on the establishment of the First IT Regime at the turn of the 19th century.Technological regimes, systemic innovation, adoption of technologies, complexity,information technology 1870-1930

Complementarity constraints and induced innovation: some evidence from the First IT Regime

Technological search is often depicted to be random. This paper takes a different view and analyses how innovative recombinant search is triggered, how it is done and what initial conditions influence the final design of technological artefacts. We argue that complementarities (non-separabilities) play an important role as focusing devices guiding the search for new combinations. Our analysis takes the perspective of technology adopters and not that of inventors or innovators of new products. We illustrate the process of decomposition and re-composition under the presence of binding complementarity constraints with a historical case study on the establishment of the First IT Regime at the turn of the 19th century.research and development ;