多数控代码解释器共存的设计与应用

当前数控系统种类繁多,各大数控系统厂商数控代码指令互不兼容。在开放式数控系统及仿真软件中越来越多地需要支持多家厂商的数控代码体系,以满足终端用户的需求。基于Lex和Yacc对一个数控系统中多数控代码解释器共存开展了研究,并在GT100型数控系统中得到了成功的应用。     

Preprocessing embedded actions

Some parser generators allow the user to attach actions, consisting of executable code, to syntax rules. Actions are usually in the local programming language, so they are simply copied into the generated parser. However, we show two situations in which it is convenient to allow actions to be in a different notation. A preprocessor is used to translate such notations into the local programming language. A preprocessor must know where to find actions and how to translate them. We show how these two activities can be programmed separately. Often, the user only has to worry about the second part: once the parser generator is known, the placement of the actions is known as well, so routines for finding actions can be separately compiled and linked in. Examples in the paper are based on the parser generator Yacc, but the approach is not limited to Yacc, or even to parser generators. Certain compositions of syntax-directed translations can be implemented by preprocessing actions.     

基于Lex和Yacc的多数控代码解释器研究与应用

数控代码解释的水平和效率是影响数控加工效率的重要因素之一.介绍了Lex和Yacc在数控代码解释方面的运用及其优越性,为了提高数控代码解释效率和准确度,降低开发成本,基于Lex和Yacc开发了支持多种数控代码的线切割数控代码解释器.在此基础上利用Qt设计了Linux下用于电火花线切割系统的多数控代码解释器用户应用程序.     

The IELR(1) algorithm for generating minimal LR(1) parser tables for non-LR(1) grammars with conflict resolution

There has been a recent effort in the literature to reconsider grammar-dependent software development from an engineering point of view. As part of that effort, we examine a deficiency in the state of the art of practical LR parser table generation. Specifically, LALR sometimes generates parser tables that do not accept the full language that the grammar developer expects, but canonical LR is too inefficient to be practical particularly during grammar development. In response, many researchers have attempted to develop minimal LR parser table generation algorithms. In this paper, we demonstrate that a well known algorithm described by David Pager and implemented in Menhir, the most robust minimal LR(1) implementation we have discovered, does not always achieve the full power of canonical LR(1) when the given grammar is non-LR(1) coupled with a specification for resolving conflicts. We also detail an original minimal LR(1) algorithm, IELR(1) (Inadequacy Elimination LR(1)), which we have implemented as an extension of GNU Bison and which does not exhibit this deficiency. Using our implementation, we demonstrate the relevance of this deficiency for several real-world parser specifications, and we demonstrate the feasibility of IELR(1). Finally, we demonstrate that, if canonical LR(1) were employed instead, grammar development would be severely impeded regardless of the power of the computer hardware.     

Parsing Non-LR(k) grammars with yacc

Of the parser generating tools currently in use, yacc (or one of its several variants) is perhaps the most frequently employed. However, because of inherent ambiguities there are some languages (such as C++) that a yacc-generated parser cannot successfully compile. This paper describes a set of minor modifications to yacc-like tools that allows them to be used in a straightforward way to parse ambiguities and, more generally, grammars that require an indefinite amount of lookahead. Required changes to the lexical analyzer are also discussed, and the application of these techniques is illustrated within the context of specific examples.     

嵌入式数据库中利用Lex,Yacc设计SQL编译器

随着嵌入式数据库系统的不断发展，对其数据查询的能力提出了新的要求。基于自行设计的嵌入式数据库系统，利用Lex和Yacc工具实现了嵌入式SQL编译器的设计，进一步对所生成的语法树进行了初步的优化研究。结果表明此编译器大大增强支持SQL查询语言的能力。     

Ytracc: A parse browser for yacc grammars

We describe a program for the display and exploration of complex, domain-specific information: ytracc, an interactive grammar debugging tool for compiler writers. The ytracc system provides the designer of a yacc grammar a method of tracing a parser as it uses the grammar, ytracc captures the states of the parse as it is carried out. The captured parse can then be replayed forwards or backwards, step-by-step, or subtree-by-subtree, as defined by the non-terminals of the grammar. The tool has been successfully used by students as an assistant in an advanced undergraduate compiler construction class, and we use the tool in our everyday work.     

基于状态回朔技术的规范LR分析算法

LR分析技术以其自身的优点在实际当中有着非常广泛的应用,但是,能够识别LR(1)语言的规范LR分析器由于其下推自动机的复杂性,其实用性受到比较大的限制.通过回朔下推自动机的状态迁移路径能够从根本上解决这一问题.主要讨论了基于状态回朔技术的规范型LR分析器的基本原理与构造技术.     

基于Lex ＆ Yacc的电火花加工译码系统

介绍了Lex ＆ Yacc工具的特点，研究基于Lex ＆ Yacc的电火花加工（EDM）译码系统的设计，以正则表达式和巴科斯范式为基础对EDM数控译码器的词法分析和语法分析作了深入探讨，最终在Linux上实现了集多功能于一体的EDM译码系统的集成开发环境。     

现代商人法溯源

本文通过对现代商人法进行追根溯源,认为现代商人法的概念是由英国的著名国际贸易法教授施米托夫最早提出来的,现代商人法起源于欧洲旧的商人习惯法,它的渊源来自商事惯例与国际立法。