The role of concurrency in an evolutionary view of programming abstractions

In this paper we examine how concurrency has been embodied in mainstream programming languages. In particular, we rely on the evolutionary talking borrowed from biology to discuss major historical landmarks and crucial concepts that shaped the development of programming languages. We examine the general development process, occasionally deepening into some language, trying to uncover evolutionary lineages related to specific programming traits. We mainly focus on concurrency, discussing the different abstraction levels involved in present-day concurrent programming and emphasizing the fact that they correspond to different levels of explanation. We then comment on the role of theoretical research on the quest for suitable programming abstractions, recalling the importance of changing the working framework and the way of looking every so often. This paper is not meant to be a survey of modern mainstream programming languages: it would be very incomplete in that sense. It aims instead at pointing out a number of remarks and connect them under an evolutionary perspective, in order to grasp a unifying, but not simplistic, view of the programming languages development process

BioScript: programming safe chemistry on laboratories-on-a-chip

This paper introduces BioScript, a domain-specific language (DSL) for programmable biochemistry which executes on emerging microfluidic platforms. The goal of this research is to provide a simple, intuitive, and type-safe DSL that is accessible to life science practitioners. The novel feature of the language is its syntax, which aims to optimize human readability; the technical contributions of the paper include the BioScript type system and relevant portions of its compiler. The type system ensures that certain types of errors, specific to biochemistry, do not occur, including the interaction of chemicals that may be unsafe. The compiler includes novel optimizations that place biochemical operations to execute concurrently on a spatial 2D array platform on the granularity of a control flow graph, as opposed to individual basic blocks. Results are obtained using both a cycle-accurate microfluidic simulator and a software interface to a real-world platform

Staattisesti tyypitetyt ohjelmointikielet JavaScript-ekosysteemissä: tyyppijärjestelmien näkökulma

JavaScript is a ubiquitous programming language with usage in web, mobile applications and server software. The status of the language as the de-facto programming language of the web has made the language ecosystem advanced with a great number of userspace libraries and major companies working on efficient runtime systems. The core language, however, has numerous known difficulties caused by the initial design and persisted by the requirements for backwards-compatibility. In the last decade, a number of programming languages have chosen JavaScript as the compile target of the language. Type theory and its application, programming language type systems, is an essential area of study in the design of programming languages. Every high-level programming language features a type system that greatly influences the ways of designing and implementing programs in the language. This thesis examines a group of selected statically-typed programming languages that compile to JavaScript. The core topics of research in this thesis are the motivation for new JS-compiled languages, the type system design of the languages, and the future direction of the JavaScript ecosystem based on the current trends and parallels to other programming ecosystems. The results of the work include identifying several trends in type systems for the JS ecosystem and the web. These include unsound yet convenient partially inferred type systems for object-oriented and multi-paradigm programming and fully inferred extended Hindley-Milner type systems for primarily functional programming languages. Additionally, different options for the advancement of the programming ecosystem, including type annotations, inference of dynamically typed languages and new compile targets, are explored. Finally, based on the design choices of the languages researched, we provide several recommendations for safe and productive statically typed programming in the JavaScript ecosystem.JavaScript on laajalti käytetty ohjelmointikieli, jonka käyttö ulottuu web- ja mobiilisovelluksiin sekä palvelinohjelmistoon. Kielen asema web-kehityksen de-facto-ohjelmointikielenä on luonut sen ympärille laajan ohjelmistoekosysteemin, joka kattaa suuren määrän ohjelmistokirjastoja sekä tehokkaita ajoympäristöjä. Itse kieli aiheuttaa tästä huolimatta vaikeuksia alkuperäisten suunnitteluvirheiden ja vaaditun taaksepäinyhteensopivuuden vuoksi. Viimeisen vuosikymmenen aikana useampi ohjelmointikieli on alkanut käyttää JavaScriptia käännöskohteenaan. Tyyppiteoria ja sen sovellus, ohjelmointikielten tyyppijärjestelmät, on tärkeä tutkimusala liittyen ohjelmointikielten suunnitteluun. Tyyppijärjestelmä on osa jokaista korkean tason ohjelmoinikieltä ja vaikuttaa täten suuresti itse ohjelmointikielen muihin ominaisuuksiin ja käyttöön. Tämä tutkimus käsittelee joukkoa staattisesti tyypitettyjä ohjelmointikieliä, jotka kääntyvät JavaScript-koodiksi. Tutkimuksen ytimessä ovat uusien kielten kehityksen motiivit, kielten tyyppijärjestelmien suunnittelu ja ominaisuudet sekä JavaScript-ekosysteemin mahdolliset tulevaisuuden suunnat. Työn tuloksena tunnistamme useita trendejä tyyppijärjestelmien suunnittelussa JavaScript-ekosysteemiin. Näihin kuuluu käytännölliset, mutta teoriassa epäturvalliset tyyppijärjestelmät olio- ja moniparadigmaohjelmoinkieliin sekä funktionaalisten ohjelmointikielien Hindley-Milner-pohjaiset tyyppijärjestelmät, joissa muuttujien tyypit pystytään täysin päättelemään ilman ohjelman kirjoittajan annotaatioita. Lisäksi nostamme esiin useita tulevaisuuden suuntia, jotka voisivat viedä JS-ekosysteemiä eteenpäin. Näihin kuuluvat tyyppiannotaatiot, dynaamisten kielten tyyppi-inferenssi ja uudet käännöskohteet web-ekosysteemiin. Lopuksi annamme tutkimuksen perusteella suosituksia ominaisuuksista ja suunnitteluratkaisuista, jotka voisivat mahdollistaa tehokkaan ja turvallisen ohjelmistokehityksen JavaScript-ekosysteemissä tulevaisuudessa

Executable Refinement Types

This dissertation introduces executable refinement types, which refine structural types by semi-decidable predicates, and establishes their metatheory and accompanying implementation techniques. These results are useful for undecidable type systems in general. Particular contributions include: (1) Type soundness and a logical relation for extensional equivalence for executable refinement types (though type checking is undecidable); (2) hybrid type checking for executable refinement types, which blends static and dynamic checks in a novel way, in some sense performing better statically than any decidable approximation; (3) a type reconstruction algorithm - reconstruction is decidable even though type checking is not, when suitably redefined to apply to undecidable type systems; (4) a novel use of existential types with dependent types to ensure that the language of logical formulae is closed under type checking (5) a prototype implementation, Sage, of executable refinement types such that all dynamic errors are communicated back to the compiler and are thenceforth static errors.Comment: Ph.D. dissertation. Accepted by the University of California, Santa Cruz, in March 2014. 278 pages (295 including frontmatter

Comparing Tag Scheme Variations Using an Abstract Machine Generator

In this paper we study, in the context of a WAM-based abstract machine for Prolog, how variations in the encoding of type information in tagged words and in their associated basic operations impact performance and memory usage. We use a high-level language to specify encodings and the associated operations. An automatic generator constructs both the abstract machine using this encoding and the associated Prolog-to-byte code compiler. Annotations in this language make it possible to impose constraints on the final representation of tagged words, such as the effectively addressable space (fixing, for example, the word size of the target processor /architecture), the layout of the tag and value bits inside the tagged word, and how the basic operations are implemented. We evaluate large number of combinations of the different parameters in two scenarios: a) trying to obtain an optimal general-purpose abstract machine and b) automatically generating a specially-tuned abstract machine for a particular program. We conclude that we are able to automatically generate code featuring all the optimizations present in a hand-written, highly-optimized abstract machine and we canal so obtain emulators with larger addressable space and better performance