Fast Flexible Function Dispatch in Julia
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UNIX and Computer Science Spreading UNIX Around the World: by Ronda Hauben an Interview with John Lions
Winter/Spring 1994 Celebrating 25 Years of UNIX Volume 6 No 1 "I believe all significant software movements start at the grassroots level. UNIX, after all, was not developed by the President of AT&T." Kouichi Kishida, UNIX Review, Feb., 1987 UNIX and Computer Science Spreading UNIX Around the World: by Ronda Hauben An Interview with John Lions [Editor's Note: This year, 1994, is the 25th anniversary of the [Editor's Note: Looking through some magazines in a local invention of UNIX in 1969 at Bell Labs. The following is university library, I came upon back issues of UNIX Review from a "Work In Progress" introduced at the USENIX from the mid 1980's. In these issues were articles by or inter- Summer 1993 Conference in Cincinnati, Ohio. This article is views with several of the pioneers who developed UNIX. As intended as a contribution to a discussion about the sig- part of my research for a paper about the history and devel- nificance of the UNIX breakthrough and the lessons to be opment of the early days of UNIX, I felt it would be helpful learned from it for making the next step forward.] to be able to ask some of these pioneers additional questions The Multics collaboration (1964-1968) had been created to based on the events and developments described in the UNIX "show that general-purpose, multiuser, timesharing systems Review Interviews. were viable." Based on the results of research gained at MIT Following is an interview conducted via E-mail with John using the MIT Compatible Time-Sharing System (CTSS), Lions, who wrote A Commentary on the UNIX Operating AT&T and GE agreed to work with MIT to build a "new System describing Version 6 UNIX to accompany the "UNIX hardware, a new operating system, a new file system, and a Operating System Source Code Level 6" for the students in new user interface." Though the project proceeded slowly his operating systems class at the University of New South and it took years to develop Multics, Doug Comer, a Profes- Wales in Australia. -
Metaobject Protocols: Why We Want Them and What Else They Can Do
Metaobject protocols: Why we want them and what else they can do Gregor Kiczales, J.Michael Ashley, Luis Rodriguez, Amin Vahdat, and Daniel G. Bobrow Published in A. Paepcke, editor, Object-Oriented Programming: The CLOS Perspective, pages 101 ¾ 118. The MIT Press, Cambridge, MA, 1993. © Massachusetts Institute of Technology All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher. Metaob ject Proto cols WhyWeWant Them and What Else They Can Do App ears in Object OrientedProgramming: The CLOS Perspective c Copyright 1993 MIT Press Gregor Kiczales, J. Michael Ashley, Luis Ro driguez, Amin Vahdat and Daniel G. Bobrow Original ly conceivedasaneat idea that could help solve problems in the design and implementation of CLOS, the metaobject protocol framework now appears to have applicability to a wide range of problems that come up in high-level languages. This chapter sketches this wider potential, by drawing an analogy to ordinary language design, by presenting some early design principles, and by presenting an overview of three new metaobject protcols we have designed that, respectively, control the semantics of Scheme, the compilation of Scheme, and the static paral lelization of Scheme programs. Intro duction The CLOS Metaob ject Proto col MOP was motivated by the tension b etween, what at the time, seemed liketwo con icting desires. The rst was to have a relatively small but p owerful language for doing ob ject-oriented programming in Lisp. The second was to satisfy what seemed to b e a large numb er of user demands, including: compatibility with previous languages, p erformance compara- ble to or b etter than previous implementations and extensibility to allow further exp erimentation with ob ject-oriented concepts see Chapter 2 for examples of directions in which ob ject-oriented techniques might b e pushed. -
MANNING Greenwich (74° W
Object Oriented Perl Object Oriented Perl DAMIAN CONWAY MANNING Greenwich (74° w. long.) For electronic browsing and ordering of this and other Manning books, visit http://www.manning.com. The publisher offers discounts on this book when ordered in quantity. For more information, please contact: Special Sales Department Manning Publications Co. 32 Lafayette Place Fax: (203) 661-9018 Greenwich, CT 06830 email: [email protected] ©2000 by Manning Publications Co. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in the book, and Manning Publications was aware of a trademark claim, the designations have been printed in initial caps or all caps. Recognizing the importance of preserving what has been written, it is Manning’s policy to have the books we publish printed on acid-free paper, and we exert our best efforts to that end. Library of Congress Cataloging-in-Publication Data Conway, Damian, 1964- Object oriented Perl / Damian Conway. p. cm. includes bibliographical references. ISBN 1-884777-79-1 (alk. paper) 1. Object-oriented programming (Computer science) 2. Perl (Computer program language) I. Title. QA76.64.C639 1999 005.13'3--dc21 99-27793 CIP Manning Publications Co. Copyeditor: Adrianne Harun 32 Lafayette -
Homework 2: Reflection and Multiple Dispatch in Smalltalk
Com S 541 — Programming Languages 1 October 2, 2002 Homework 2: Reflection and Multiple Dispatch in Smalltalk Due: Problems 1 and 2, September 24, 2002; problems 3 and 4, October 8, 2002. This homework can either be done individually or in teams. Its purpose is to familiarize you with Smalltalk’s reflection facilities and to help learn about other issues in OO language design. Don’t hesitate to contact the staff if you are not clear about what to do. In this homework, you will adapt the “multiple dispatch as dispatch on tuples” approach, origi- nated by Leavens and Millstein [1], to Smalltalk. To do this you will have to read their paper and then do the following. 1. (30 points) In a new category, Tuple-Smalltalk, add a class Tuple, which has indexed instance variables. Design this type to provide the necessary methods for working with dispatch on tuples, for example, we’d like to have access to the tuple of classes of the objects in a given tuple. Some of these methods will depend on what’s below. Also design methods so that tuples can be used as a data structure (e.g., to pass multiple arguments and return multiple results). 2. (50 points) In the category, Tuple-Smalltalk, design other classes to hold the behavior that will be declared for tuples. For example, you might want something analogous to a method dictionary and other things found in the class Behavior or ClassDescription. It’s worth studying those classes to see what can be adapted to our purposes. -
To Type Or Not to Type: Quantifying Detectable Bugs in Javascript
To Type or Not to Type: Quantifying Detectable Bugs in JavaScript Zheng Gao Christian Bird Earl T. Barr University College London Microsoft Research University College London London, UK Redmond, USA London, UK [email protected] [email protected] [email protected] Abstract—JavaScript is growing explosively and is now used in to invest in static type systems for JavaScript: first Google large mature projects even outside the web domain. JavaScript is released Closure1, then Microsoft published TypeScript2, and also a dynamically typed language for which static type systems, most recently Facebook announced Flow3. What impact do notably Facebook’s Flow and Microsoft’s TypeScript, have been written. What benefits do these static type systems provide? these static type systems have on code quality? More concretely, Leveraging JavaScript project histories, we select a fixed bug how many bugs could they have reported to developers? and check out the code just prior to the fix. We manually add The fact that long-running JavaScript projects have extensive type annotations to the buggy code and test whether Flow and version histories, coupled with the existence of static type TypeScript report an error on the buggy code, thereby possibly systems that support gradual typing and can be applied to prompting a developer to fix the bug before its public release. We then report the proportion of bugs on which these type systems JavaScript programs with few modifications, enables us to reported an error. under-approximately quantify the beneficial impact of static Evaluating static type systems against public bugs, which type systems on code quality. -
Towards Practical Runtime Type Instantiation
Towards Practical Runtime Type Instantiation Karl Naden Carnegie Mellon University [email protected] Abstract 2. Dispatch Problem Statement Symmetric multiple dispatch, generic functions, and variant type In contrast with traditional dynamic dispatch, the runtime of a lan- parameters are powerful language features that have been shown guage with multiple dispatch cannot necessarily use any static in- to aid in modular and extensible library design. However, when formation about the call site provided by the typechecker. It must symmetric dispatch is applied to generic functions, type parameters check if there exists a more specific function declaration than the may have to be instantiated as a part of dispatch. Adding variant one statically chosen that has the same name and is applicable to generics increases the complexity of type instantiation, potentially the runtime types of the provided arguments. The process for deter- making it prohibitively expensive. We present a syntactic restriction mining when a function declaration is more specific than another is on generic functions and an algorithm designed and implemented for laid out in [4]. A fully instantiated function declaration is applicable the Fortress programming language that simplifies the computation if the runtime types of the arguments are subtypes of the declared required at runtime when these features are combined. parameter types. To show applicability for a generic function we need to find an instantiation that witnesses the applicability and the type safety of the function call so that it can be used by the code. Formally, given 1. Introduction 1. a function signature f X <: τX (y : τy): τr, J K Symmetric multiple dispatch brings with it several benefits for 2. -
A Trusted Mechanised Javascript Specification
A Trusted Mechanised JavaScript Specification Martin Bodin Arthur Charguéraud Daniele Filaretti Inria & ENS Lyon Inria & LRI, Université Paris Sud, CNRS Imperial College London [email protected] [email protected] d.fi[email protected] Philippa Gardner Sergio Maffeis Daiva Naudžiunien¯ e˙ Imperial College London Imperial College London Imperial College London [email protected] sergio.maff[email protected] [email protected] Alan Schmitt Gareth Smith Inria Imperial College London [email protected] [email protected] Abstract sation was crucial. Client code that works on some of the main JavaScript is the most widely used web language for client-side ap- browsers, and not others, is not useful. The first official standard plications. Whilst the development of JavaScript was initially just appeared in 1997. Now we have ECMAScript 3 (ES3, 1999) and led by implementation, there is now increasing momentum behind ECMAScript 5 (ES5, 2009), supported by all browsers. There is the ECMA standardisation process. The time is ripe for a formal, increasing momentum behind the ECMA standardisation process, mechanised specification of JavaScript, to clarify ambiguities in the with plans for ES6 and 7 well under way. ECMA standards, to serve as a trusted reference for high-level lan- JavaScript is the only language supported natively by all major guage compilation and JavaScript implementations, and to provide web browsers. Programs written for the browser are either writ- a platform for high-assurance proofs of language properties. ten directly in JavaScript, or in other languages which compile to We present JSCert, a formalisation of the current ECMA stan- JavaScript. -
TAMING the MERGE OPERATOR a Type-Directed Operational Semantics Approach
Technical Report, Department of Computer Science, the University of Hong Kong, Jan 2021. 1 TAMING THE MERGE OPERATOR A Type-directed Operational Semantics Approach XUEJING HUANG JINXU ZHAO BRUNO C. D. S. OLIVEIRA The University of Hong Kong (e-mail: fxjhuang, jxzhao, [email protected]) Abstract Calculi with disjoint intersection types support a symmetric merge operator with subtyping. The merge operator generalizes record concatenation to any type, enabling expressive forms of object composition, and simple solutions to hard modularity problems. Unfortunately, recent calculi with disjoint intersection types and the merge operator lack a (direct) operational semantics with expected properties such as determinism and subject reduction, and only account for terminating programs. This paper proposes a type-directed operational semantics (TDOS) for calculi with intersection types and a merge operator. We study two variants of calculi in the literature. The first calculus, called li, is a variant of a calculus presented by Oliveira et al. (2016) and closely related to another calculus by Dunfield (2014). Although Dunfield proposes a direct small-step semantics for her calcu- lus, her semantics lacks both determinism and subject reduction. Using our TDOS we obtain a direct + semantics for li that has both properties. The second calculus, called li , employs the well-known + subtyping relation of Barendregt, Coppo and Dezani-Ciancaglini (BCD). Therefore, li extends the more basic subtyping relation of li, and also adds support for record types and nested composition (which enables recursive composition of merged components). To fully obtain determinism, both li + and li employ a disjointness restriction proposed in the original li calculus. -
BCL: a Cross-Platform Distributed Data Structures Library
BCL: A Cross-Platform Distributed Data Structures Library Benjamin Brock, Aydın Buluç, Katherine Yelick University of California, Berkeley Lawrence Berkeley National Laboratory {brock,abuluc,yelick}@cs.berkeley.edu ABSTRACT high-performance computing, including several using the Parti- One-sided communication is a useful paradigm for irregular paral- tioned Global Address Space (PGAS) model: Titanium, UPC, Coarray lel applications, but most one-sided programming environments, Fortran, X10, and Chapel [9, 11, 12, 25, 29, 30]. These languages are including MPI’s one-sided interface and PGAS programming lan- especially well-suited to problems that require asynchronous one- guages, lack application-level libraries to support these applica- sided communication, or communication that takes place without tions. We present the Berkeley Container Library, a set of generic, a matching receive operation or outside of a global collective. How- cross-platform, high-performance data structures for irregular ap- ever, PGAS languages lack the kind of high level libraries that exist plications, including queues, hash tables, Bloom filters and more. in other popular programming environments. For example, high- BCL is written in C++ using an internal DSL called the BCL Core performance scientific simulations written in MPI can leverage a that provides one-sided communication primitives such as remote broad set of numerical libraries for dense or sparse matrices, or get and remote put operations. The BCL Core has backends for for structured, unstructured, or adaptive meshes. PGAS languages MPI, OpenSHMEM, GASNet-EX, and UPC++, allowing BCL data can sometimes use those numerical libraries, but are missing the structures to be used natively in programs written using any of data structures that are important in some of the most irregular these programming environments. -
Safejava: a Unified Type System for Safe Programming
SafeJava: A Unified Type System for Safe Programming by Chandrasekhar Boyapati B.Tech. Indian Institute of Technology, Madras (1996) S.M. Massachusetts Institute of Technology (1998) Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 2004 °c Massachusetts Institute of Technology 2004. All rights reserved. Author............................................................................ Chandrasekhar Boyapati Department of Electrical Engineering and Computer Science February 2, 2004 Certified by........................................................................ Martin C. Rinard Associate Professor, Electrical Engineering and Computer Science Thesis Supervisor Accepted by....................................................................... Arthur C. Smith Chairman, Department Committee on Graduate Students SafeJava: A Unified Type System for Safe Programming by Chandrasekhar Boyapati Submitted to the Department of Electrical Engineering and Computer Science on February 2, 2004, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract Making software reliable is one of the most important technological challenges facing our society today. This thesis presents a new type system that addresses this problem by statically preventing several important classes of programming errors. If a program type checks, we guarantee at compile time that the program -
Julia: a Fresh Approach to Numerical Computing
RSDG @ UCL Julia: A Fresh Approach to Numerical Computing Mosè Giordano @giordano [email protected] Knowledge Quarter Codes Tech Social October 16, 2019 Julia’s Facts v1.0.0 released in 2018 at UCL • Development started in 2009 at MIT, first • public release in 2012 Julia co-creators won the 2019 James H. • Wilkinson Prize for Numerical Software Julia adoption is growing rapidly in • numerical optimisation, differential equations, machine learning, differentiable programming It is used and taught in several universities • (https://julialang.org/teaching/) Mosè Giordano (RSDG @ UCL) Julia: A Fresh Approach to Numerical Computing October 16, 2019 2 / 29 Julia on Nature Nature 572, 141-142 (2019). doi: 10.1038/d41586-019-02310-3 Mosè Giordano (RSDG @ UCL) Julia: A Fresh Approach to Numerical Computing October 16, 2019 3 / 29 Solving the Two-Language Problem: Julia Multiple dispatch • Dynamic type system • Good performance, approaching that of statically-compiled languages • JIT-compiled scripts • User-defined types are as fast and compact as built-ins • Lisp-like macros and other metaprogramming facilities • No need to vectorise: for loops are fast • Garbage collection: no manual memory management • Interactive shell (REPL) for exploratory work • Call C and Fortran functions directly: no wrappers or special APIs • Call Python functions: use the PyCall package • Designed for parallelism and distributed computation • Mosè Giordano (RSDG @ UCL) Julia: A Fresh Approach to Numerical Computing October 16, 2019 4 / 29 Multiple Dispatch using DifferentialEquations -
Balancing the Eulisp Metaobject Protocol
Balancing the EuLisp Metaob ject Proto col x y x z Harry Bretthauer and Harley Davis and Jurgen Kopp and Keith Playford x German National Research Center for Computer Science GMD PO Box W Sankt Augustin FRG y ILOG SA avenue Gallieni Gentilly France z Department of Mathematical Sciences University of Bath Bath BA AY UK techniques which can b e used to solve them Op en questions Abstract and unsolved problems are presented to direct future work The challenge for the metaob ject proto col designer is to bal One of the main problems is to nd a b etter balance ance the conicting demands of eciency simplicity and b etween expressiveness and ease of use on the one hand extensibili ty It is imp ossible to know all desired extensions and eciency on the other in advance some of them will require greater functionality Since the authors of this pap er and other memb ers while others require greater eciency In addition the pro of the EuLisp committee have b een engaged in the design to col itself must b e suciently simple that it can b e fully and implementation of an ob ject system with a metaob ject do cumented and understo o d by those who need to use it proto col for EuLisp Padget and Nuyens intended This pap er presents a metaob ject proto col for EuLisp to correct some of the p erceived aws in CLOS to sim which provides expressiveness by a multileveled proto col plify it without losing any of its p ower and to provide the and achieves eciency by static semantics for predened means to more easily implement it eciently The current metaob