Left Recursion in Parsing Expression Grammars

Parsing Expression Grammars (PEGs) are a formalism that can describe all deterministic context-free languages through a set of rules that specify a top-down parser for some language. PEGs are easy to use, and there are efficient implementations of PEG libraries in several programming languages. A frequently missed feature of PEGs is left recursion, which is commonly used in Context-Free Grammars (CFGs) to encode left-associative operations. We present a simple conservative extension to the semantics of PEGs that gives useful meaning to direct and indirect left-recursive rules, and show that our extensions make it easy to express left-recursive idioms from CFGs in PEGs, with similar results. We prove the conservativeness of these extensions, and also prove that they work with any left-recursive PEG. PEGs can also be compiled to programs in a low-level parsing machine. We present an extension to the semantics of the operations of this parsing machine that let it interpret left-recursive PEGs, and prove that this extension is correct with regards to our semantics for left-recursive PEGs.Comment: Extended version of the paper "Left Recursion in Parsing Expression Grammars", that was published on 2012 Brazilian Symposium on Programming Language

The Analysis of design and manufacturing tasks using haptic and immersive VR - Some case studies

The use of virtual reality in interactive design and manufacture has been researched extensively but the practical application of this technology in industry is still very much in its infancy. This is surprising as one would have expected that, after some 30 years of research commercial applications of interactive design or manufacturing planning and analysis would be widespread throughout the product design domain. One of the major but less well known advantages of VR technology is that logging the user gives a great deal of rich data which can be used to automatically generate designs or manufacturing instructions, analyse design and manufacturing tasks, map engineering processes and, tentatively, acquire expert knowledge. The authors feel that the benefits of VR in these areas have not been fully disseminated to the wider industrial community and - with the advent of cheaper PC-based VR solutions - perhaps a wider appreciation of the capabilities of this type of technology may encourage companies to adopt VR solutions for some of their product design processes. With this in mind, this paper will describe in detail applications of haptics in assembly demonstrating how user task logging can lead to the analysis of design and manufacturing tasks at a level of detail not previously possible as well as giving usable engineering outputs. The haptic 3D VR study involves the use of a Phantom and 3D system to analyse and compare this technology against real-world user performance. This work demonstrates that the detailed logging of tasks in a virtual environment gives considerable potential for understanding how virtual tasks can be mapped onto their real world equivalent as well as showing how haptic process plans can be generated in a similar manner to the conduit design and assembly planning HMD VR tool reported in PART A. The paper concludes with a view as to how the authors feel that the use of VR systems in product design and manufacturing should evolve in order to enable the industrial adoption of this technology in the future

Living with MND: An Evaluation of Care Pathways Available to Adults with, and the Families or Carers of Adults with Motor Neurone Disease in Scotland

Main Findings Motor Neurone Disease (MND) is a progressive condition that damages motor neurones, the cells that control voluntary muscle activity, in both the spinal cord and the brain. It can cause difficulty in walking and movement, talking, swallowing and breathing and many muscles in the body can become affected. To find out what it is like to live with MND from the perspective of those with the condition we carried out a longitudinal study in which we interviewed 40 people with MND and their partners a number of times over a two year period. We found that: Control, or more particularly the lack of it was the overarching theme that occurred throughout the interviews. People wanted to be consulted, informed and involved in decisions about their health and their social care and where this happened people were more likely to report satisfaction with the service. The diagnosis of MND is a long and protracted process, one that was for many a very distressing experience. 45% of those we spoke to took over 12 months for a diagnosis, 19% over 18 months. Participants had difficulty getting professionals to take their symptoms seriously and once they entered the neurology system many people experienced delays and often the diagnosis was not confirmed by a neurologist. Physical access to hospitals was in some cases difficult. Car parking and the location of the clinic often made it hard for people to get to a hospital appointment. Health professionals had an important role. Good professionals were those who took time to create a sense of teamwork with the person with MND and their family. This was less likely to happen with hospital consultants and where this did not people felt insecure and not listened to. There was also some evidence of poor communication between professionals and medical notes were often not shared between different professionals. Where people accessed general wards they were rarely treated well. Informal carers provided much of the social care and support for those with MND, with spouses meeting most of the need. Whilst many people were happy with this arrangement meeting the need placed a great deal of strain on the families. Many people did not want to rely on care supplied by outside agencies as they did not trust the quality or the reliability of the care and neither did they want their home overrun with people. Housing adaptations and the provision of aids to daily living were for many a great cause of stress and strain and many people felt that they were not involved in the decision making process, felt out of control and unable to influence the situation. The rapidly progressive nature of MND can exacerbate this problem. Social Care and support provided by local authorities was very heavily criticised. There were inconsistencies between services, people felt excluded from decisions made about their care and their care needs and people did not have access to the necessary information to make an informed choice about which services to access. Specialist Care Nurses (SCN) played a vital role in the care and support of those with MND. Not only do they provide help and support directly they also help to act as a champion for the family and coordinate services and service provision. This service is however under great strain and there are a significant number of people for whom this service is not working because the service was too stretched and the resources were not available to allow the SCN to meet their needs

IMPACT, Fall 2012

https://scholarworks.sjsu.edu/impact/1004/thumbnail.jp

Pattern matching in compilers

In this thesis we develop tools for effective and flexible pattern matching. We introduce a new pattern matching system called amethyst. Amethyst is not only a generator of parsers of programming languages, but can also serve as an alternative to tools for matching regular expressions. Our framework also produces dynamic parsers. Its intended use is in the context of IDE (accurate syntax highlighting and error detection on the fly). Amethyst offers pattern matching of general data structures. This makes it a useful tool for implementing compiler optimizations such as constant folding, instruction scheduling, and dataflow analysis in general. The parsers produced are essentially top-down parsers. Linear time complexity is obtained by introducing the novel notion of structured grammars and regularized regular expressions. Amethyst uses techniques known from compiler optimizations to produce effective parsers.Comment: master thesi