Session Arrows: a Session-Type Based Framework for Parallel Code Generation
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No-Longer-Foreign: Teaching an ML Compiler to Speak C “Natively”
Electronic Notes in Theoretical Computer Science 59 No. 1 (2001) URL: http://www.elsevier.nl/locate/entcs/volume59.html 16 pages No-Longer-Foreign: Teaching an ML compiler to speak C “natively” Matthias Blume 1 Lucent Technologies, Bell Laboratories Abstract We present a new foreign-function interface for SML/NJ. It is based on the idea of data- level interoperability—the ability of ML programs to inspect as well as manipulate C data structures directly. The core component of this work is an encoding of the almost 2 complete C type sys- tem in ML types. The encoding makes extensive use of a “folklore” typing trick, taking advantage of ML’s polymorphism, its type constructors, its abstraction mechanisms, and even functors. A small low-level component which deals with C struct and union declarations as well as program linkage is hidden from the programmer’s eye by a simple program-generator tool that translates C declarations to corresponding ML glue code. 1 An example Suppose you are an ML programmer who wants to link a program with some C rou- tines. The following example (designed to demonstrate data-level interoperability rather than motivate the need for FFIs in the first place) there are two C functions: input reads a list of records from a file and findmin returns the record with the smallest i in a given list. The C library comes with a header file ixdb.h that describes this interface: typedef struct record *list; struct record { int i; double x; list next; }; extern list input (char *); extern list findmin (list); Our ml-nlffigen tool translates ixdb.h into an ML interface that corre- sponds nearly perfectly to the original C interface. -
Causal Commutative Arrows Revisited
Causal Commutative Arrows Revisited Jeremy Yallop Hai Liu University of Cambridge, UK Intel Labs, USA [email protected] [email protected] Abstract init which construct terms of an overloaded type arr. Most of the Causal commutative arrows (CCA) extend arrows with additional code listings in this paper uses these combinators, which are more constructs and laws that make them suitable for modelling domains convenient for defining instances, in place of the notation; we refer such as functional reactive programming, differential equations and the reader to Paterson (2001) for the details of the desugaring. synchronous dataflow. Earlier work has revealed that a syntactic Unfortunately, speed does not always follow succinctness. Al- transformation of CCA computations into normal form can result in though arrows in poetry are a byword for swiftness, arrows in pro- significant performance improvements, sometimes increasing the grams can introduce significant overhead. Continuing with the ex- speed of programs by orders of magnitude. In this work we refor- ample above, in order to run exp, we must instantiate the abstract mulate the normalization as a type class instance and derive op- arrow with a concrete implementation, such as the causal stream timized observation functions via a specialization to stream trans- transformer SF (Liu et al. 2009) that forms the basis of signal func- formers to demonstrate that the same dramatic improvements can tions in the Yampa domain-specific language for functional reactive be achieved without leaving the language. programming (Hudak et al. 2003): newtype SF a b = SF {unSF :: a → (b, SF a b)} Categories and Subject Descriptors D.1.1 [Programming tech- niques]: Applicative (Functional) Programming (The accompanying instances for SF , which define the arrow operators, appear on page 6.) Keywords arrows, stream transformers, optimization, equational Instantiating exp with SF brings an unpleasant surprise: the reasoning, type classes program runs orders of magnitude slower than an equivalent pro- gram that does not use arrows. -
What I Wish I Knew When Learning Haskell
What I Wish I Knew When Learning Haskell Stephen Diehl 2 Version This is the fifth major draft of this document since 2009. All versions of this text are freely available onmywebsite: 1. HTML Version http://dev.stephendiehl.com/hask/index.html 2. PDF Version http://dev.stephendiehl.com/hask/tutorial.pdf 3. EPUB Version http://dev.stephendiehl.com/hask/tutorial.epub 4. Kindle Version http://dev.stephendiehl.com/hask/tutorial.mobi Pull requests are always accepted for fixes and additional content. The only way this document will stayupto date and accurate through the kindness of readers like you and community patches and pull requests on Github. https://github.com/sdiehl/wiwinwlh Publish Date: March 3, 2020 Git Commit: 77482103ff953a8f189a050c4271919846a56612 Author This text is authored by Stephen Diehl. 1. Web: www.stephendiehl.com 2. Twitter: https://twitter.com/smdiehl 3. Github: https://github.com/sdiehl Special thanks to Erik Aker for copyediting assistance. Copyright © 20092020 Stephen Diehl This code included in the text is dedicated to the public domain. You can copy, modify, distribute and perform thecode, even for commercial purposes, all without asking permission. You may distribute this text in its full form freely, but may not reauthor or sublicense this work. Any reproductions of major portions of the text must include attribution. The software is provided ”as is”, without warranty of any kind, express or implied, including But not limitedtothe warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authorsor copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, Arising from, out of or in connection with the software or the use or other dealings in the software. -
Idris: a Functional Programming Language with Dependent Types
Programming Languages and Compiler Construction Department of Computer Science Christian-Albrechts-University of Kiel Seminar Paper Idris: A Functional Programming Language with Dependent Types Author: B.Sc. Finn Teegen Date: 20th February 2015 Advised by: M.Sc. Sandra Dylus Contents 1 Introduction1 2 Fundamentals2 2.1 Universes....................................2 2.2 Type Families..................................2 2.3 Dependent Types................................3 2.4 Curry-Howard Correspondence........................4 3 Language Overview5 3.1 Simple Types and Functions..........................5 3.2 Dependent Types and Functions.......................6 3.3 Implicit Arguments...............................7 3.4 Views......................................8 3.5 Lazy Evaluation................................8 3.6 Syntax Extensions...............................9 4 Theorem Proving 10 4.1 Propositions as Types and Terms as Proofs................. 10 4.2 Encoding Intuitionistic First-Order Logic................... 12 4.3 Totality Checking................................ 14 5 Conclusion 15 ii 1 Introduction In conventional Hindley-Milner based programming languages, such as Haskell1, there is typically a clear separation between values and types. In dependently typed languages, however, this distinction is less clear or rather non-existent. In fact, types can depend on arbitrary values. Thus, they become first-class citizens and are computable like any other value. With types being allowed to contain values, they gain the possibility to describe prop- erties of their own elements. The standard example for dependent types is the type of lists of a given length - commonly referred to as vectors - where the length is part of the type itself. When starting to encode properties of values as types, the elements of such types can be seen as proofs that the stated property is true. -
An Exploration of the Effects of Enhanced Compiler Error Messages for Computer Programming Novices
Technological University Dublin ARROW@TU Dublin Theses LTTC Programme Outputs 2015-11 An Exploration Of The Effects Of Enhanced Compiler Error Messages For Computer Programming Novices Brett A. Becker Technological University Dublin Follow this and additional works at: https://arrow.tudublin.ie/ltcdis Part of the Computer and Systems Architecture Commons, and the Educational Methods Commons Recommended Citation Becker, B. (2015) An exploration of the effects of enhanced compiler error messages for computer programming novices. Thesis submitted to Technologicl University Dublin in part fulfilment of the requirements for the award of Masters (M.A.) in Higher Education, November 2015. This Theses, Masters is brought to you for free and open access by the LTTC Programme Outputs at ARROW@TU Dublin. It has been accepted for inclusion in Theses by an authorized administrator of ARROW@TU Dublin. For more information, please contact [email protected], [email protected]. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License An Exploration of the Effects of Enhanced Compiler Error Messages for Computer Programming Novices A thesis submitted to Dublin Institute of Technology in part fulfilment of the requirements for the award of Masters (M.A.) in Higher Education by Brett A. Becker November 2015 Supervisor: Dr Claire McDonnell Learning Teaching and Technology Centre, Dublin Institute of Technology Declaration I certify that this thesis which I now submit for examination for the award of Masters (M.A.) in Higher Education is entirely my own work and has not been taken from the work of others, save and to the extent that such work has been cited and acknowledged within the text of my own work. -
Directing Javascript with Arrows
Directing JavaScript with Arrows Khoo Yit Phang Michael Hicks Jeffrey S. Foster Vibha Sazawal University of Maryland, College Park {khooyp,mwh,jfoster,vibha}@cs.umd.edu Abstract callback with a (short) timeout. Unfortunately, this style of event- JavaScript programmers make extensive use of event-driven pro- driven programming is tedious, error-prone, and hampers reuse. gramming to help build responsive web applications. However, The callback sequencing code is strewn throughout the program, standard approaches to sequencing events are messy, and often and very often each callback must hard-code the names of the next lead to code that is difficult to understand and maintain. We have events and callbacks in the chain. found that arrows, a generalization of monads, are an elegant solu- To combat this problem, many researchers and practitioners tion to this problem. Arrows allow us to easily write asynchronous have developed libraries to ease the construction of rich and highly programs in small, modular units of code, and flexibly compose interactive web applications. Examples include jQuery (jquery. them in many different ways, while nicely abstracting the details of com), Prototype (prototypejs.org), YUI (developer.yahoo. asynchronous program composition. In this paper, we present Ar- com/yui), MochiKit (mochikit.com), and Dojo (dojotoolkit. rowlets, a new JavaScript library that offers arrows to the everyday org). These libraries generally provide high-level APIs for com- JavaScript programmer. We show how to use Arrowlets to construct mon features, e.g., drag-and-drop, animation, and network resource a variety of state machines, including state machines that branch loading, as well as to handle API differences between browsers. -
The Glasgow Haskell Compiler User's Guide, Version 4.08
The Glasgow Haskell Compiler User's Guide, Version 4.08 The GHC Team The Glasgow Haskell Compiler User's Guide, Version 4.08 by The GHC Team Table of Contents The Glasgow Haskell Compiler License ........................................................................................... 9 1. Introduction to GHC ....................................................................................................................10 1.1. The (batch) compilation system components.....................................................................10 1.2. What really happens when I “compile” a Haskell program? .............................................11 1.3. Meta-information: Web sites, mailing lists, etc. ................................................................11 1.4. GHC version numbering policy .........................................................................................12 1.5. Release notes for version 4.08 (July 2000) ........................................................................13 1.5.1. User-visible compiler changes...............................................................................13 1.5.2. User-visible library changes ..................................................................................14 1.5.3. Internal changes.....................................................................................................14 2. Installing from binary distributions............................................................................................16 2.1. Installing on Unix-a-likes...................................................................................................16 -
SOME USEFUL STRUCTURES for CATEGORICAL APPROACH for PROGRAM BEHAVIOR in Computer Science, Where We Often Use More Complex Structures Not Expressible by Sets
JIOS, VOL. 35, NO. 1 (2011) SUBMITTED 02/11; ACCEPTED 03/11 UDC 004.423.45 [ SomeSome useful Useful structures Structures for categorical for Categorical approach Approach for program for Programbehavior Behavior Viliam Slodicákˇ [email protected] Department of Computers and Informatics Faculty of Electrical Engineering and Informatics Technical university of Košice Letná 9, 042 00 Košice Slovak Republic Abstract Using of category theory in computer science has extremely grown in the last decade. Categories allow us to express mathematical structures in unified way. Algebras are used for constructing basic structures used in computer programs. A program can be considered as an element of the initial algebra arising from the used programming language. In our contribution we formulate two ways of expressing algebras in categories. We also construct the codomain functor from the arrow category of algebras into the base category of sets which objects are also the carrier-sets of the algebras. This functor expresses the relation between algebras and carrier-sets. Keywords: Algebra, arrow category, monad, Kleisli category, codomain functor 1. Introduction Knowing and proving of the expected behavior of complex program systems is very important and actual rôle. It carries the time and cost savings: in mathematics [8] or in practical applications of economical character. The aim of programming is to construct such correct programs and program systems that during their execution provide expected behavior [7]. A program can be considered as an element of the initial algebra arising from the used programming language [14]. Algebraic structures and number systems are widely used in computer science. -
The Bluej Environment Reference Manual
The BlueJ Environment Reference Manual Version 2.0 for BlueJ Version 2.0 Kasper Fisker Michael Kölling Mærsk Mc-Kinney Moller Institute University of Southern Denmark HOW DO I ... ? – INTRODUCTION ........................................................................................................ 1 ABOUT THIS DOCUMENT................................................................................................................................. 1 RELATED DOCUMENTS.................................................................................................................................... 1 REPORT AN ERROR.......................................................................................................................................... 1 USING THE CONTEXT MENU........................................................................................................................... 1 1 PROJECTS.......................................................................................................................................... 2 1.1 CREATE A NEW PROJECT................................................................................................................... 2 1.2 OPEN A PROJECT ............................................................................................................................... 2 1.3 FIND OUT WHAT A PROJECT DOES .................................................................................................... 2 1.4 COPY A PROJECT .............................................................................................................................. -
Constrained Type Families (Extended Version)
Constrained Type Families (extended version) J. GARRETT MORRIS, e University of Edinburgh and e University of Kansas 42 RICHARD A. EISENBERG, Bryn Mawr College We present an approach to support partiality in type-level computation without compromising expressiveness or type safety. Existing frameworks for type-level computation either require totality or implicitly assume it. For example, type families in Haskell provide a powerful, modular means of dening type-level computation. However, their current design implicitly assumes that type families are total, introducing nonsensical types and signicantly complicating the metatheory of type families and their extensions. We propose an alternative design, using qualied types to pair type-level computations with predicates that capture their domains. Our approach naturally captures the intuitive partiality of type families, simplifying their metatheory. As evidence, we present the rst complete proof of consistency for a language with closed type families. CCS Concepts: •eory of computation ! Type structures; •So ware and its engineering ! Func- tional languages; Additional Key Words and Phrases: Type families, Type-level computation, Type classes, Haskell ACM Reference format: J. Garre Morris and Richard A. Eisenberg. 2017. Constrained Type Families (extended version). PACM Progr. Lang. 1, 1, Article 42 (January 2017), 38 pages. DOI: hp://dx.doi.org/10.1145/3110286 1 INTRODUCTION Indexed type families (Chakravarty et al. 2005; Schrijvers et al. 2008) extend the Haskell type system with modular type-level computation. ey allow programmers to dene and use open mappings from types to types. ese have given rise to further extensions of the language, such as closed type families (Eisenberg et al. -
Companion Object
1. Functional Programming Functional Programming What is functional programming? What is it good for? Why to learn it? Functional Programming Programs as a composition of pure functions. Pure function? Deterministic. Same result for the same inputs. Produces no observable side eects. fun mergeAccounts(acc1: Account, acc2: Account): Account = Account(acc1.balance + acc2.balance) val mergedAcc = mergeAccounts(Account(500), Account(1000)) Target platform: JVM Running on Arrow v. 0.11.0-SNAPSHOT Running on Kotlin v. 1.3.50 Referential Transparency Function can be replaced with its corresponding value without changing the program's behavior. Based on the substitution model. Referential Transparency Better reasoning about program behavior. Pure functions referentially transparent. Substitution model Replace a named reference (function) by its value. Based on equational reasoning. Unlocks local reasoning. fun add(a: Int, b: Int): Int = a + b val two = add(1, 1) // could be replaced by 2 everywhere in the program val equal = (two == 1 + 1) Target platform: JVM Running on Arrow v. 0.11.0-SNAPSHOT Running on Kotlin v. 1.3.50 Substitution model Same example, but with two Accounts. fun mergeAccounts(acc1: Account, acc2: Account): Account = Account(acc1.balance + acc2.balance) val mergedAcc = mergeAccounts(Account(100), Account(200)) // could be replaced by Account(300) everywhere // in the program val equal = (mergedAcc == Account(300)) Target platform: JVM Running on Arrow v. 0.11.0-SNAPSHOT Running on Kotlin v. 1.3.50 Side eect? Function tries to access or modify the external world. val accountDB = AccountDB() fun mergeAccounts(acc1: Account, acc2: Account): Account { val merged = Account(acc1.balance + acc2.balance) accountDB.remove(listOf(acc1, acc2)) // side effect! accountDB.save(merged) // side effect! return merged } val merged = mergeAccounts(Account(100), Account(400)) Target platform: JVM Running on Arrow v. -
It's All About Morphisms
It’s All About Morphisms Uberto Barbini @ramtop https://medium.com/@ramtop About me OOP programmer Agile TDD Functional PRogramming Finance Kotlin Industry Blog: https://medium.com/@ ramtop Twitter: @ramtop #morphisms#VoxxedVienna @ramtop Map of this presentation Monoid Category Monad Functor Natural Transformation Yoneda Applicative Morphisms all the way down... #morphisms#VoxxedVienna @ramtop I don’t care about Monads, why should I? Neither do I what I care about is y el is to define system behaviour ec Pr #morphisms#VoxxedVienna @ramtop This presentation will be a success if most of you will not fall asleep #morphisms#VoxxedVienna @ramtop This presentation will be a success if You will consider that Functional Programming is about transformations and preserving properties. Not (only) lambdas and flatmap #morphisms#VoxxedVienna @ramtop What is this Category thingy? Invented in 1940s “with the goal of understanding the processes that preserve mathematical structure.” “Category Theory is about relation between things” “General abstract nonsense” #morphisms#VoxxedVienna @ramtop Once upon a time there was a Category of Stuffed Toys and a Category of Tigers... #morphisms#VoxxedVienna @ramtop A Category is defined in 5 steps: 1) A collection of Objects #morphisms#VoxxedVienna @ramtop A Category is defined in 5 steps: 2) A collection of Arrows #morphisms#VoxxedVienna @ramtop A Category is defined in 5 steps: 3) Each Arrow works on 2 Objects #morphisms#VoxxedVienna @ramtop A Category is defined in 5 steps: 4) Arrows can be combined #morphisms#VoxxedVienna