如何在lex中获得正则表达式的这种模式匹配 [英] How to get such pattern matching of regular expression in lex

问题描述

我想检查正则表达式中的特定模式，但是我做不到.输入应该像

Hi I want to check a specific pattern in regular expression but I'm failed to do that. Input should be like

名词 单词名称:单词含义

我成功获取了名词和 wordname ，但是无法设计出单词含义的模式.我的代码是:

I'm successful getting noun and wordname but couldn't design a pattern for word meaning. My code is :

int state;
char *meaning;
char *wordd; 

^verb   { state=VERB; }
^adj    { state = ADJ; }
^adv    { state = ADV; }
^noun   { state = NOUN; }
^prep   { state = PREP; }
^pron   { state = PRON; }
^conj   { state = CONJ; }

//my try but failed
[:\a-z]   {
meaning=yytext;
printf(" Meaning is getting detected %s", meaning);

}

[a-zA-Z]+  {
word=yytext;

}

示例输入:

noun john:This is a name

现在word应该等于john，meaning应该等于This is a name.

Now word should be equal to john and meaning should be equal to This is a name.

推荐答案

同意采用lex状态(也称为开始条件)(奇怪，但没有有用的教程)

Agreeing that lex states (also known as start conditions) are the way to go (odd, but there are no useful tutorials).

简而言之:

• 您的应用程序可以组织为州，其中一个用于名词"，一个用于"john"，另一个用于定义(在冒号之后).
在lex文件顶部的

• 声明状态，例如

• your application can be organized as states, using one for "noun", one for "john" and one for the definition (after the colon).

• at the top of the lex file, declare the states, e.g.,

%s TYPE NAME VALUE

您的程序在操作中使用BEGIN()宏来切换状态，例如，

your program switches states using the BEGIN() macro, in actions, e.g.,

{ BEGIN(TYPE); }

在NAME状态下，您的词法分析器会查找您认为名称应为的任何内容，例如

in the NAME state, your lexer looks for whatever you think a name should be, e.g.,

<NAME>[[:alpha:]][[:alnum:]]+ { my_name = strdup(yytext); }

名称以冒号结尾，所以

<NAME>":" { BEGIN(VALUE); }

该值就是直到行尾的所有内容，例如

the value is then everything until the end of the line, e.g.,

<VALUE>.* { my_value = strdup(yytext); BEGIN(INITIAL); }

进一步阅读:

• 开始条件(flex文档)
• Flex简介

• Start conditions (flex documentation)
• Introduction to Flex

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