Issues in programming language design

This is the 23rd Self-Assessment Procedure. 1 The purpose of this procedure is to let its readers test their knowledge of some of the more important features of significant programming languages. The features of imperative languages like Fortran, Algol 60, PL/I, Pascal, Modula-2, C, and Ada considered are data types, data structures, control structures, program units, scope of names, and parameter passing. Some of the corresponding features of functional languages like Lisp, logic programming languages like Prolog, and ohject-oriented programming languages like C++ and Smalltalk, are reviewed. Finally brief consideration is given to syntax and semantics, chiefly by reference to the Backus-Naur form, BNF. The features of programming languages affect all aspects of programming, including the ease of writing and maintaining programs, the reliahility of software, and the efficiency and portability of programs. Knowledge of programming language concepts and constructs is of importance to software developers, programmers, and designers of programming languages and compilers. The topic of this procedure should be of interest to any computer science student or practitioner who wishes to test his or her knowledge and learn more about one of the most important and broad areas in the computer field. The language used most often in the questions is Pascal, with Ada, Lisp, and Prolog also featured prominently. A glossary is included which defines some of the terms used in the procedure. The questions are either multiple-choice or short answer. Some of the multiple-choice questions allow for more than one correct answer.

Program design languages: How much detail should they include?

Why do some programming languages fail and others succeed? What does the answer tell us about programming language design, implementation, and principles? To help answer these and other questions, we argue for examining the sociological groundings of programming language theory: socio-PLT.Researchers in the social sciences have studied adoption in many contexts. We show how their findings are applicable to programming language design. For example, many programming language features provide benefits that programmers cannot directly or immediately observe and therefore may not find compelling. From clean water to safe sex, the health community has repeatedly identified and surmounted similar observability barriers. We use such results from outside of programming language theory to frame a research agenda that should help us understand the social foundations of languages. Finally, we examine implications of our approach, such as for the design space of language features and the assessment of scientific research into programming languages.

At the University of Tennessee at Martin (UTM), freshman computer science majors were being successful in their first quarter in computer science, but many majors were not completing the year sequence (Programming Concepts and Problem Solving I, II, and III). This study describes a freshman studies program that helps increase student retention in the first computer science course.Two populations were used in this study. The first population (Group A) consisted of 25 freshman computer science majors (16 men and 9 women) enrolled Fall Quarter 85 in freshman orientation General Studies GS1000 for one quarter hour credit. The second population (Group B) consisted of 17 freshman computer science majors (12 men and 5 women) enrolled the Fall Quarter 86 in freshman orientation General Studies GS1001 for two quarter hours credit. Both groups were placed in the first course in computer science using the cutting scores ACT English > 17 or 0.78 (ACT English) + 0.49 (UTM Math Placement) > 33. Both Groups A and B had an average ACT English score of 20 and an average UTM Math Placement score of 55. Each quarter during the freshman year, the computer science major enrolls in calculus (4 hrs.), Programming Concepts and Problem Solving (3 hrs.), a laboratory science (4 hrs.), English (3 hrs.), and a humanities course (3 hrs.).Group A was offered a freshman orientation program that involved a pass/fail one quarter hour credit GS1000 which met one hour each day during freshman studies week. Each section consisted of twenty-five heterogeneously grouped students. The course content was review of study skills. Group B was offered a freshman orientation program that involved a pass/fail two quarter hour credit GS1001 which met one hour each day during freshman studies week, plus one hour each week during the first quarter. Each section consisted of only students of a particular major (computer science) and was taught by a faculty member of that department. The topics of this course consisted of a review of study skills, discussions of student problems, special academic speakers, field trips to professional sites, cultural events, meetings with deans and department heads, and a follow-up on study skills. In the meeting before the final exam week, the faculty member dealt specifically with suggestions on preparing for finals.Groups A and B were enrolled in the same first computer science sequence (Programming Concepts and Problem Solving I, II, and III) their freshman year. Both groups had the same instructors, text (Introduction to Computing and Computer Science with Pascal by H. Walker), and course syllabus for this sequence. Both groups carried the same academic course load their freshman year. However, in Group A only 20% (5 out of 25) of the students completed the first computer science sequence with a grade of C or better, while in Group B 41% (7 out of 17) completed the same sequence with a grade of C or better. Student retention is achieved through the students' integration into the academic and social systems of the college by two factors: (1) faculty-student interaction and (2) peer-group interaction. Although the population of this study was small, I believe GS1001 provides one way of increasing student retention in computer science.

There has long been a close association between research in software engineering and the design of programming languages. Part of the IMPACT project involves an exploration of the interrelations of these two fields and documentation in a report of how fundamental research in software engineering has been a valuable resource for programming language features commonly used today. The resulting report investigates the relationship by considering features in currently used languages, including exceptions, control and data abstractions, types, inheritance, concurrency and visualization mechanisms.This paper, exerpted from the report, focuses on the influence of software engineering research on the development of exceptions. The paper demonstrates that there is a symbiotic relationship between software engineering research and the design of exception handing in programming languages. Publication of these partial results is aimed at soliciting feedback and comments from both the programming languages and software engineering communities.

The mainstream approach to design of BDI-inspired agent programming languages is to choose a set of agent-oriented features with a particular semantics and their subsequent implementation in the programming language interpreter. The language designer's choices thus impose strong constraints on the architecture of the implemented agents as well as only a limited toolbox of high-level language constructs for encoding the agent program. As an alternative, we propose a purely syntactic approach to designing an agent programming language. On the substrate of Behavioural State Machines (BSM ), a generic modular programming language for hybrid agents, we show how an agent designer can implement high-level agent-oriented constructs in the form of code patterns (macros). To express the semantics of agent programs in the logic-agnostic programming language of BSM, we propose LTL program annotations and subsequently introduce DCTL*, an extension of the CTL* logic with features of dynamic logic, for reasoning about traces of BSM program executions. We show how DCTL* specifications can be used to prove relevant properties of code patterns. Moreover, DCTL* allows for natural verification of BSM agent programs.

Christopher Strachey’s paper on Fundamental Concepts in Programming Languages is being published here for the first time. Written in the autumn of 1967, it is based on the lectures given by Strachey at an International School in Computer Programming, held in Copenhagen in August 1967. Strachey intended the paper to be published in the proceedings of the School—but the proceedings never materialized, and Strachey’s paper has remained an unpublished preprint for more than three decades. It is, however, one of Strachey’s most significant and lengthy papers; widely circulated in the original typescript version, it has also been highly influential. Strachey’s paper starts with some philosophical remarks about the need to focus on semantic issues in the design of programming languages, and to “recognise and isolate the central concepts—things analogous to the concepts of continuity and convergence in analysis”. Strachey then proceeds to give a clear and incisive exposition of many of his insights into programming language design and formal semantics, covering the following main topics: r assignment commands, Land R-values; r expression evaluation and environments; r commands and sequencing; r modes of parameter-passing and variable binding; r functions and routines as data items; r types and (parametric) polymorphism; and r compound data structures and pointers.

This volume contains the proceedings of the 21th Brazilian Symposium on Programing Languages (SBLP 2017), held during September 21-22, 2017, at Fortaleza, Brazil. SBLP is a well-established symposium, promoted by the Brazilian Computer Society since 1996, and provides a venue for researchers and practitioners interested in the fundamental principles and innovations in the design and implementation of programming languages and systems. Since 2010, SBLP has been organized in the context of CBSoft (Brazilian Conference on Software: Theory and Practice), colocated with a number of other events on computer science and software engineering.

Hundreds of programming languages are in use todayscripting languages for Internet commerce, user interface programming tools, spreadsheet macros, page format specification languages, and many others. Designing a programming language is a metaprogramming activity that bears certain similarities to programming in a regular language, with clarity and simplicity even more important than in ordinary programming. This comprehensive text uses a simple and concise framework to teach key ideas in programming language design and implementation. The book's unique approach is based on a family of syntactically simple pedagogical languages that allow students to explore programming language concepts systematically. It takes as its premise and starting point the idea that when language behaviors become incredibly complex, the description of the behaviors must be incredibly simple. The book presents a set of tools (a mathematical metalanguage, abstract syntax, operational and denotational semantics) and uses it to explore a comprehensive set of programming language design dimensions, including dynamic semantics (naming, state, control, data), static semantics (types, type reconstruction, polymporphism, effects), and pragmatics (compilation, garbage collection). The many examples and exercises offer students opportunities to apply the foundational ideas explained in the text. Specialized topics and code that implements many of the algorithms and compilation methods in the book can be found on the book's Web site, along with such additional material as a section on concurrency and proofs of the theorems in the text. The book is suitable as a text for an introductory graduate or advanced undergraduate programming languages course; it can also serve as a reference for researchers and practitioners.

PLACES 2015 (full title: Programming Language Approaches to Concurrency- and Communication-Centric Software) is the eighth edition of the PLACES workshop series. After the first PLACES, which was affiliated to DisCoTec in 2008, the workshop has been part of ETAPS every year since 2009 and is now an established part of the ETAPS satellite events. PLACES 2015 was held on 18th April in London, UK. The workshop series was started in order to promote the application of novel programming language ideas to the increasingly important problem of developing software for systems in which concurrency and communication are intrinsic aspects. This includes software for both multi-core systems and large-scale distributed and/or service-oriented systems. The scope of PLACES includes new programming language features, whole new programming language designs, new type systems, new semantic approaches, new program analysis techniques, and new implementation mechanisms. This volume consists of revised versions of the papers that were presented at the workshop.

PLACES 2017 (full title: Programming Language Approaches to Concurrency- and\nCommunication-cEntric Software) is the tenth edition of the PLACES workshop\nseries. After the first PLACES, which was affiliated to DisCoTec in 2008, the\nworkshop has been part of ETAPS every year since 2009 and is now an established\npart of the ETAPS satellite events. PLACES 2017 was held on 29th April in\nUppsala, Sweden. The workshop series was started in order to promote the\napplication of novel programming language ideas to the increasingly important\nproblem of developing software for systems in which concurrency and\ncommunication are intrinsic aspects. This includes software for both multi-core\nsystems and large-scale distributed and/or service-oriented systems. The scope\nof PLACES includes new programming language features, whole new programming\nlanguage designs, new type systems, new semantic approaches, new program\nanalysis techniques, and new implementation mechanisms. This volume consists of\nthe papers accepted for presentation at the workshop.\n

Approaches for programming language design used commonly in the research community today center around theoretical and performance-oriented evaluation. Recently, researchers have been considering more approaches to language design, including the use of quantitative and qualitative user studies that examine how different designs might affect programmers. In this paper, we argue for an interdisciplinary approach that incorporates many different methods in the creation and evaluation of programming languages. We argue that the addition of user-oriented design techniques can be helpful at many different stages in the programming language design process.

Type theories, logical frameworks and meta-languages form a common foundation\nfor designing, implementing, and reasoning about formal languages and their\nsemantics. They are central to the design of modern programming languages,\ncertified software, and domain specific logics. More generally, they continue\nto influence applications in many areas in mathematics, logic and computer\nscience.\n The Logical Frameworks and Meta-languages: Theory and Practice workshop aims\nto bring together designers, implementers, and practitioners working on these\nareas, and in particular about: the automation and implementation of the\nmeta-theory of programming languages and related calculi; the design of proof\nassistants, automated theorem provers, and formal digital libraries building\nupon logical framework technology; theoretical and practical issues concerning\nthe encoding of variable binding and fresh name generation, especially the\nrepresentation of, and reasoning about, datatypes defined from binding\nsignatures; case studies of meta-programming, and the mechanization of the\n(meta) theory of descriptions of programming languages and other calculi.\n This volume contains the final and revised versions of the papers presented\nat LFMTP 2010, which was held on July 14, 2010 in Edinburgh (UK). LFMTP 2010\nwas part of the Federated Logic Conference (FLoC 2010), and affilated with LICS\n2010.\n

Three key forces are shaping the modern Computer Science (CS) curriculum: (1) new topics/courses are squeezing out existing ones; (2) a focus on "big picture" and interdisciplinary aspects of CS is leading to curricula in which the traditional core courses + electives model is being superseded by a more flexible approach based on tracks/threads; and (3) project-based courses are increasingly relying on a notion of just-in-time teaching in which particular skills are not bundled into a particular course, but are covered at a point when they are needed for particular project work. The undergraduate programming language curriculum is feeling the pressure of these forces. Core courses on programming languages and compilers are being changed to electives, relegated to a software/systems track, or phased out altogether. Particular programming languages and programming language concepts are being taught in a more piecemeal fashion on an as-needed basis. Unfortunately, these changes make it increasingly likely that CS majors can graduate without being exposed to certain "big ideas" of programming languages. Programming languages (along with many other subdisciplines of CS) contains ideas that every well-educated computer scientist needs to know and which are relevant to a wide variety of projects/careers. In a CS curriculum based on tracks and projects, how can we ensure that vital intellectual components are not lost in the shuffle? One way to think about this problem is to view the CS curriculum as a collection of aspects that can be combined in different arrangements to produce various projects/courses. In this paper, we consider the benefits and challenges of an aspect-oriented view of the CS curriculum, particularly in regard to programming language concepts.

In recent years, the programming language design community has engaged in rigorous debate on the role of empirical evidence in the design of general purpose programming languages. Some scholars contend that the language community has failed to embrace a form of evidence that is non-controversial in other disciplines (e.g., medicine, biology, psychology, sociology, physics, chemistry), while others argue that a science of language design is unrealistic. While the discussion will likely persist for some time, we begin here a systematic evaluation of the use of empirical evidence with human users, documenting, paper-by-paper, the evidence provided for human factors decisions, beginning with 359 papers from the workshops PPIG, Plateau, and ESP. This preliminary work provides the following contributions: an analysis of the 1) overall quantity and quality of empirical evidence used in the workshops, and of the 2) overall significant challenges to reliably coding academic papers. We hope that, once complete, this long-term research project will serve as a practical catalog designers can use when evaluating the impact of a language feature on human users.