Repairing syntax errors in LR parsers

Despite the popularity of LALR(1) parser generators such as Yacc/Bison and LL parser generators such as ANTLR, robust and effective LR(1) parser generators are rare due to expensive performance and implementation difficulty. This work employed relevant algorithms, including the Knuth canonical algorithm, Pager's practical general method, lane-tracing algorithm, unit production elimination algorithm and its extension, and the edge-pushing algorithm, implemented an efficient, practical and Yacc/Bison-compatible open-source parser generator Hyacc, which supports full LR(0)/LALR(1)/LR(1) and partial LR(k). Based on the implementation, an empirical study was conducted comparing different LR(1) parser generation algorithms and LALR(1) algorithms. The result shows that LR(1) parser generation based upon improved algorithms and carefully selected data structures can be sufficiently efficient to be of practical use with modern computing facilities.

A YACC extension for LRR grammar parsing

A compiler generator called Metauncle is introduced. Metauncle produces one-pass compilers in which all attributes are evaluated in conjunction with LR parsing. The description of a language is given to Metauncle as an L-attributed grammar, and the system transforms it before generation of an evaluator to another attribute grammar satisfying the requirements for evaluation. The transformed grammar belongs to the class of so-called uncle-attributed grammars. Besides general information about the system, the definition of uncle-attributed grammars, the idea of the grammar transformation and the default rules of the specification language are presented.

The combination of modern programming languages and partial evaluation yields new approaches to old problems. In particular, the combination of functional programming and partial evaluation can turn a general parser into a parser generator. We use an inherently functional approach to implement general LR( k ) parsers and specialize them with respect to the input grammars using offline partial evaluation. The functional specification of LR parsing yields a concise implementation of the algorithms themselves. Furthermore, we demonstrate the elegance of the functional approach by incorporating on-the-fly attribute evaluation for S-attributed grammars and two schemes for error recovery, which lend themselves to natural and elegant implementation. The parser require only minor changes to achieve good specialization results. The generated parsers have production quality and match those produced by traditional parser generators in sped and compactness

In this paper, we present a probabilistic shift-reduce parsing model which can overcome low context-sensitivity of previous LR parsing models. Since previous models are restricted by LR parsing framework, they can utilize only a lookahead and a LR state (stack). The proposed model is not restricted by LR parsing framework, and is able to add rich contextual information as needed. To show an example of contextual information designed for applying the proposed model to Korean, we devise a new context scheme named “surface-context-types” which uses syntactic structures, sentential forms, and selective lexicals. Experimental results show that rich contextual information used by our model can improve the parsing accuracy, and our model outperforms the previous models even when using a lookahead alone.

A unifying model for lookahead LR parsing

Practical arbitrary lookahead LR parsing

The test results obtained on 24 externally-pressurised torispherical steel shells are given in this paper. The knuckle radius-to-diameter ratio of the domes varied from 0.06 to 0.18 and the spherical cap radius-to-thickness ratios were between 75 and 335. Initial shape and thickness measurements were carried out on all the torispheres and a summary of this information is given. The BOSOR 5 shell buckling program was employed to predict the buckling/collapse pressures of all the domes; both perfect domes and those with axisymmetric imperfections were considered. The correlation between the theoretical predictions and the experimental results was, in general, very good. The main conclusions of the present investigation are: (i) that some of the experimental buckling pressures were lower than those obtained by multiplying the BS 5500 design values by a safety factor of 1.5, and (ii) that those torispheres with sharp knuckle radii failed by plastic collapse in the knuckle region and the collapse pressures were not very sensitive to initial geometric imperfections. It thus appears that the BS 5500 rules relating to the strength of shallow torispheres subjected to external pressure need to be amended, and that the tolerances on geometric shape for cases which are likely to be imperfection-insensitive should be reconsidered.

This paper describes the comparison between experimental and computational results for the flow in an inlet system that contains a plenum. Here, the main focus is on the details of the computations and the comparison with experimental results for flow in the plenum. Details of the experiment are described elsewhere. By varying mesh density, boundary conditions, discretization schemes and turbulence models, a wide-ranging study of the accuracy of computational techniques for an industrial problem has been made. In particular, levels of mesh refinement for converged numerical solutions have been determined, together with performance levels for the various settings used. In terms of velocity prediction, when the flow is driven by boundary conditions specified at the outlet more accurate results are achieved. This is due to the flow at the inlet being calculated more accurately in these cases. The effects of different discretization schemes and turbulence models on the velocity predictions are small. Pressure predictions are, however, improved by more complex turbulence models such as the renormalization group (RNG) model.

The traditional repair process is slow in the repair process, the materials used in the construction process are relatively expensive, the fire performance is poor, and the wet paving construction effect is not good. Therefore, a new technology for rapid repair of reinforced concrete piers is studied. Combined with the maintenance process, the section of the existing reinforced concrete bridge pier is repaired; on the basis of the repair process, the reinforcement sleeve of the reinforced concrete pier is repaired; the feasibility of the designed repair technology is verified by simulation experiment. The experimental results show that the bridge pier repair technology can quickly and effectively realize the overall reinforcement of reinforced concrete pier, with less consumables, low cost, small steel section thickness and good repair effect.

The adsorption of alkylpyridinium surfactants on Aerosil OX50 silica has been studied as a function of surfactant concentration, aliphatic chain length, pH, and ionic strength in solution. The adsorption isotherms are complemented by electrophoretic mobility measurements. The experimental results have been compared with calculations based on the SCFA theory for adsorption on a charge-regulating surface. The experimental results and SCFA calculations both show that the isotherms of the cationic surfactant on silica, obtained at different salt concentrations, have a common intersection point (cip). As was shown before by surface charge adaptation experiments and is now confirmed by the theoretical calculations, aliphatic segments have a moderate affinity to the surface due to hydrophobic interactions. These interactions result in a flat orientation of the surfactant molecules in the adsorbed layer. The shape of the adsorption isotherms depends on the salt concentration. The first pseudoplateau observed at low salt concentrations vanishes at high salt concentration. At low salt concentrations, electrostatic repulsions between “head-on” adsorbed headgroups and local crowding prevent the aggregation process in the adsorbed layer and inhibit further adsorption in the region of the first pseudoplateau. At high salt concentrations, the adsorption starts later due to the screening of the surface charge by the salt ions, and it increases steeper due to the diminished lateral repulsions between surfactant molecules. The common intersection point in the isotherms measured at different salt concentrations marks the transition from a flat monolayer to a flat bilayer.

The effective interplay of simulation and experimental results for analysis and optimization of microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting lasers (VCSELs) operating at wavelength around 1.55 mum is presented. The VCSEL combines a MEMS with concave Al-GaAs-GaAs mirror membrane and an InP-based active cavity with tunnel junction aperture in a hybrid two-chip assembly. Using electrothermal MEMS actuation the included air-gap can be expanded and the cavity resonance can be tuned to longer wavelengths. The experimental results are compared with the theoretical results provided by VELM (VCSEL ELectroMagnetic), the efficient code based on the coupled mode model and adapted for the first time to handle curved-mirror geometries. The vectorial code is found to be able to fully reproduce the experimental results, such as device tuning range, modal frequency splitting, threshold gains and modal selectivity.

Various applications like finding Web communities, detecting the structure of social networks, and even analyzing a graph’s structure to uncover Internet attacks are just some of the applications for which community detection is important. In this paper, we propose an algorithm that finds the entire community structure of a network, on the basis of local interactions between neighboring nodes and an unsupervised distributed hierarchical clustering algorithm. The novelty of the proposed approach, named SCCD (standing for synthetic coordinate community detection), lies in the fact that the algorithm is based on the use of Vivaldi synthetic network coordinates computed by a distributed algorithm. The current paper not only presents an efficient distributed community finding algorithm, but also demonstrates that synthetic network coordinates could be used to derive efficient solutions to a variety of problems. Experimental results and comparisons with other methods from the literature are presented for a variety of benchmark graphs with known community structure, derived from varying a number of graph parameters and real data set graphs. The experimental results and comparisons to existing methods with similar computation cost on real and synthetic data sets demonstrate the high performance and robustness of the proposed scheme.

The objective of this paper is to provide design data of fin-tube heat exchanger which have a large diameter oval tube for dryer application. In this study, the heat transfer and pressure drop performance characteristics of the fin-tube heat exchanger were compared with Dittus-Boelter and a new correlation equation using Wilson plot method. The simulation results based on section by section method were compared with experimental results. These results showed that a new correlation equation using Wilson plot method provided better prediction, about 3 to 12%, than the Dittus-Boelter equation, from the experiment comparison. Also, the pressure drop of simulation results showed much more deviation with the experimental results.

Composite particle optimization with hyper-reflection scheme in dynamic environments