上下文无关文法（Context-Free Grammar, CFG）是一个4元组G=(V, T, S, P)，其中，V和T是不相交的有限集，S∈V，P是一组有限的产生式规则集，形如A→α，其中A∈V，且α∈(V∪T)*。V的元素称为非终结符，T的元素称为终结符，S是一个特殊的非终结符，称为文法开始符。 设G=(V, T, S, P)是一个CFG，则G产生的语言是所有可由G产生的字符串组成的集合，即L(G)={x∈T* | Sx}。一个语言L是上下文无关语言（Context-Free Language, CFL），当且仅当存在一个CFG G，使得L=L(G)。 *⇒ 例如，设文法G：S→AB A→aA|a B→bB|b 则L(G)={a^nb^m | n,m>=1} 其中非终结符都是大写字母，开始符都是S，终结符都是小写字母。
标签： Context-Free Grammar CFG
上传时间： 2013-12-10
上传用户：gaojiao1999
一:需求分析 1. 问题描述 魔王总是使用自己的一种非常精练而抽象的语言讲话,没人能听懂,但他的语言是可逐步解释成人能听懂的语言,因为他的语言是由以下两种形式的规则由人的语言逐步抽象上去的: ----------------------------------------------------------- (1) a---> (B1)(B2)....(Bm) (2)[(op1)(p2)...(pn)]---->[o(pn)][o(p(n-1))].....[o(p1)o] ----------------------------------------------------------- 在这两种形式中,从左到右均表示解释.试写一个魔王语言的解释系统,把 他的话解释成人能听得懂的话. 2. 基本要求: 用下述两条具体规则和上述规则形式(2)实现.设大写字母表示魔王语言的词汇 小写字母表示人的语言的词汇 希腊字母表示可以用大写字母或小写字母代换的变量.魔王语言可含人的词汇. (1) B --> tAdA (2) A --> sae 3. 测试数据: B(ehnxgz)B 解释成 tsaedsaeezegexenehetsaedsae若将小写字母与汉字建立下表所示的对应关系,则魔王说的话是:"天上一只鹅地上一只鹅鹅追鹅赶鹅下鹅蛋鹅恨鹅天上一只鹅地上一只鹅". | t | d | s | a | e | z | g | x | n | h | | 天 | 地 | 上 | 一只| 鹅 | 追 | 赶 | 下 | 蛋 | 恨 |
上传时间： 2014-12-02
上传用户：jkhjkh1982
The Bad Beginning: A Terrible Tale Do you enjoy happy endings? If so, The Bad Beginning by Lemony Snicket is a book you’ll want to avoid. This is a story with a bad beginning, a bad middle and a bad ending. Why would anyone want to read such a thoroughly bad book? It’s all in good fun!
标签： Beginning The Bad Terrible
上传时间： 2013-12-28
上传用户：笨小孩
This the second tutorial of the Writing Device Drivers series. There seems to be a lot of interest in the topic, so this article will pick up where the first left off. The main focus of these articles will be to build up little by little the knowledge needed to write device drivers. In this article, we will be building on the same example source code used in part one. In this article, we will expand on that code to include Read functionality, Handle Input/Ouput Controls also known as IOCTLs, and learn a bit more about IRPs.
标签： the interest tutorial Drivers
上传时间： 2016-01-28
上传用户：lmeeworm
The XML Toolbox converts MATLAB data types (such as double, char, struct, complex, sparse, logical) of any level of nesting to XML format and vice versa. For example, >> project.name = MyProject >> project.id = 1234 >> project.param.a = 3.1415 >> project.param.b = 42 becomes with str=xml_format(project, off ) "<project> <name>MyProject</name> <id>1234</id> <param> <a>3.1415</a> <b>42</b> </param> </project>" On the other hand, if an XML string XStr is given, this can be converted easily to a MATLAB data type or structure V with the command V=xml_parse(XStr).
标签： converts Toolbox complex logical
上传时间： 2016-02-12
上传用户：a673761058
GNU ccScript is a C++ class framework for creating a virtual machine execution system for use with and as a scripting/assembler language for state-transition driven realtime systems. The most common example of this is as the core of the scripting engine found in GNU Bayonne.
标签： framework for execution ccScript
上传时间： 2013-12-18
上传用户：sssl
OBPM是一个开源，轻量级的BPM系统。它的目标是让非IT人员也可以轻松构建IT业务处理流程。OBPM内建工作流引擎（Workflow Engine）, Form构建器，Report设计器。
上传时间： 2016-08-08
上传用户：evil
汉诺塔！！！ Simulate the movement of the Towers of Hanoi puzzle Bonus is possible for using animation eg. if n = 2 A→B A→C B→C if n = 3 A→C A→B C→B A→C B→A B→C A→C
标签： the animation Simulate movement
上传时间： 2017-02-11
上传用户：waizhang
Genetic Algorithm example using Java You have 10 cards numbered 1 to 10. You have to divide them into 2 piles so that: The sum of the first pile is as close as possible to 36 and the product of all in second pile is as close as poss to 360.
标签： have Algorithm You numbered
上传时间： 2017-03-08
上传用户：lacsx
function to compute an expression using int value parameters throw an exception of type illegalParameterValue in case one of the parameters is <= 0
标签： illegalPara expression parameters exception
上传时间： 2014-01-20
上传用户：a6697238
