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No description available.

A record type is a data type consisting of a collection of named fields that combines the flexibility of associative arrays in some dynamically typed languages with the safety guarantees and possible runtime performance of static typing. The structural typing of records is especially suitable for handling semi-structured data such as JSON and XML making efficient records an attractive choice for high-performance computing and large- scale data analytics. It has proven difficult to implement record types in Scala however. Existing libraries suffer from either severe compile-time penalties, large runtime over- head, or other restrictions in usability such as poor IDE integration and hard-to-compre- hend error-messages. This thesis provides a systematic description and comparison of both existing and possible new approaches to records in Scala and Dotty, a new compiler for the Scala 3 language. A novel benchmarking suite is presented, built on top of the Java Microbench- mark Harness (JMH), for measuring runtime and compile-time performance of records running on the Java Virtual Machine and currently supporting Scala, Dotty, Java and Whiteoak. To achieve field access times comparable to nominally typed classes, it is conjectured that width subtyping has to be restricted to explicit coercion and a compilation scheme for such record types is sketched. For unordered record types with width and depth sub- typing however, hashmap-based approaches are found to have the most attractive run- time performance characteristics. In particular, Dotty provides native support for such an implementation using structural refinement types that might strike a good balance be- tween flexibility and runtime performance for records in the future. / En record-typ är en datatyp som består av en en uppsättning namngivna fält som kombinerarflexibiliteten hos associativa arrayer i vissa dynamiskt typade programmeringsspråkmed säkerhetsgarantierna och den potentiella exekveringshastigheten som fås av statisk typning. Records strukturella typning är särskilt väl lämpad för att hantera semistruktureraddata såsom JSON och XML vilket gör beräkningseffektiva records ett attraktivt val för högprestandaberäkningar och storskalig dataanalys. Att implementera records i programmeringsspråket Scala har dock visat sig svårt. Existerande bibliotek lider antingenav långa kompileringstider, långsam exekveringshastighet, eller andra problem med användbarheten såsom dålig integration med olika utvecklingsmiljöer och svårförståddafelmeddelanden. Den här uppsatsen ger en systematisk beskrivning och jämförelse av både existerandeoch nya lösningar för records i Scala och Dotty, en ny kompilator för Scala 3. Ett nyttbenchmarkingverktyg för att mäta exekveringshastigheten och kompileringstiden av recordssom körs på den virtuella Java maskinen presenteras. Benchmarkingverktyget ärbyggt på Java Microbenchmark Harness (JMH) och stöder i nuläget Scala, Dotty, Java ochWhiteoak. För att åstadkomma körtider som är jämförbara med nominellt typade klasser antasatt subtypning på bredden måste begränsas till explicita konverteringsanrop och enskiss till en kompileringsstrategi för sådana records presenteras.  För record-typer med ickeordnade fält och subtypning på bredden och djupet visar sig istället records baseradepå hashtabeller ha de mest attraktiva exekveringstiderna. Dotty tillhandahåller stöd fören sådan implementation med strukturella förfiningstyper som kan komma att träffa enbra balans mellan flexibilitet och exekveringshastighet för records i framtiden.

In a world where computers are a part of most people's everyday life, learning how to instruct one to perform time consumingand/or complex tasks is beneficial. Visual programming languages aim to make the experience for people programmingcomputers the best it can be by bypassing some of the issues of syntax and translation from mental plan to executable program. However, text-based languages come out on top when it comes to the programming languages most used. This paper aims at finding the strengths and weaknesses of teaching a visual programming language to novices in order to contribute to the otherwise lacking empirical evidence within the field of teaching computer programming. The methods used in order to collect data and answer the research question took inspiration from methods used in ethnomethodology. These methods were: observation through participation within a group of programming novices and semi-structured interviews with programming tutors. What can be seen from the study is that visual programming languages offer a quick introduction to the world of programming that in many ways plays down the difficulties within the area by making programming playful and creative. On the other hand, the boundaries of the language are quickly reached and require the students to switch to a text based language. Also, the visual programming language did not help the students learn how to plan and troubleshoot theirprograms. When progressing to a text-based programming language where planning and troubleshooting are required steps ofthe process this may become troublesome. / I en värld där datorer är en del av människors vardag är det fördelaktigt att lära sig att instruera datorer att utföra tidskrävandeoch/eller komplexa uppgifter. Visuella programmeringsspråk syftar till att göra upplevelsen för personer som programmerar så bra som möjligt genom att minska fokuset på syntax och översättning från mental plan till körbart program. Men de mest använda programmeringsspråken är idag de textbaserade språken och inte de visuella. Denna uppsats syftar till att hitta styrkor och svagheter i att lära ut ett visuellt programmeringsspråk för nybörjare för att bidra till bristen på empiriska bevis inom området datorprogrammeringsundervisning. De metoder som användes för att samla data och svara på forskningsfrågantog inspiration från metoder som används inom ethnomethodologi. Dessa metoder var: observation genom deltagande i engrupp av programmeringsnybörjare samt halvstrukturerade intervjuer med programmeringshandledare. Vad som kan konstaterats från resultatet samt diskussionen är att visuella programmeringsspråk erbjuder en snabb introduktion till programmeringsvärlden och på många sätt avdramatiserar området genom att göra programmeringen lekfull och kreativ. Negativa aspekter av att använda visuella programmeringsspråk är å andra sidan att gränserna för språket snabbt nås och kräver att studenterna byter till t.ex. ett textbaserat språk. Det visuella programmeringsspråket hjälpte inte heller eleverna att lära sig att planera och felsöka sina program. När man går vidare till ett textbaserat programmeringsspråk där planering och felsökning krävs steg i processen kan det bli besvärligt.

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No description available.

The classes of simple and weak precedence grammars are generalized to include ε-rules (productions with the empty right parts). The descriptive power of epsilon simple precedence (ESP) grammars increases directly with the number of ε-rules permitted; the class of ESP grammars with no ε-rules, ESP0, is identical to the class of simple precedence grammars; ESP grammars with at most one ε-rule, ESP1, define a class of languages which properly includes the class of ESP0 languages, but is itself properly included in the class of deterministic, context-free languages. In general, ESP grammars having at most i ε-rules, ESPi, define a class of languages which is properly included in that defined by ESPi+1 grammars. This hierarchy of languages exhausts the deterministic context-free languages. The hierarchy of ESP languages is established using an iteration theorem which may be used to show that a given language is not ESPi for a given i. An algorithm to convert arbitrary LR(1) grammars to equivalent epsilon weak precedence (EWP) grammars is developed. The class of Viable Prefix EWP grammars is defined and it is shown that the EWP parser for every Viable Prefix EWP grammar detects syntactic errors at the earliest possible time. Also, it is established that every deterministic context-free language is defined by some Viable Prefix EWP grammar. Finally, it is shown that the class of EWP grammars, while properly containing the class of Viable Prefix EWP grammars, is itself properly included in the well-known classes of context-free grammars with the ε-rules which define exactly the deterministic context-free languages.

As modern industrial robots are used more in industry, the need for qualified programmers and operators will increase. Inexpensive robots are available for use as training systems, but these robots typically lack the high level tools, such as high level, languages and graphics simulators, that are available for the industrial robots. A high level programming language and a graphics simulator were developed for one of these training robots, the Heath ET-18 Hero Robot. The programs were designed to be executed on an IBM Personal Computer. The software was developed as part of an overall system which also includes a compiler and a program for downloading software to the Hero over a serial interface.

<p> In this day and age, many companies struggle with the maintenance of legacy scientific software systems written in outdated programming languages. These languages use low-level control structures, algorithmic operations and cumbersome syntax that make the true meaning of an algorithm difficult to understand. To make matters worse, the process of reverse engineering the algorithm to specification often involves a considerable amount of manual work which is error-prone and time-consuming.</p> <p> This thesis explores a completely automated method of reverse engineering. We apply this method to FORTRAN77 linear algebra software. This software is transformed to an extension of FORTRAN77, which we call Fortran-M. This language allows for high-level mathematical constructs such as sums, products and vector and matrix operations. To serve as a proof-of-concept for this method, we have developed a tool which uses a combination of pattern matching on the source code's abstract syntax tree to recognise low-level control structures, and symbolic analysis to determine the meaning of loops. Once a pattern has been recognised, or a loop's invariant found, we apply transformations to the syntax tree, thus creating a Fortran-M equivalent.</p> / Thesis / Master of Applied Science (MASc)

Although some success has been achieved in the design of front-end natural language processors to data base management systems, transporting the processor to various data base management systems has proven to be elusive. A transportable system must be modular; it must be able to adapt to radically different data domains; and it must be able to communicate with many different data managers. The system developed accomplishes this by maintaining its own knowledge base distinct from the target data base management system, so that no communication is needed between the natural language processor and the data manager during the parse. The knowledge base is developed by interviewing the system administrator about the structure and meaning of the elements in the target data base. The natural language processor then converts the natural language query into an unambiguous intermediate-language query, which is easily converted to P the target query language using simple syntactic methods. / Master of Science