使用正则表达式匹配和提取数据

Posted 2023-02-21

【中文标题】使用正则表达式匹配和提取数据

【英文标题】：Matching and Extracting data using regular expression

【发布时间】：2015-11-14 17:36:06

【问题描述】：

问题：找到匹配的字符串并从匹配的字符串中提取数据。有许多带有关键字和数据的命令字符串。

命令示例：

问名字给我打电话 通知执行此操作的名称 请求的消息名称

关键字：询问、通知、消息、到、那个。数据：

输入字符串：

让彼得给我打电话 通知珍娜我要离开了 给家里发消息说我迟到了

我的问题包括两个问题 1) 查找匹配命令 2) 提取数据

这是我正在做的事情： 我创建了多个正则表达式： "问[[:s:]][[:w:]]+[[:s:]]到[[:s:]][[:w:]]+" 或 "问([^\t\ n]+?)到([^\t\n]+?)" "通知[[:s:]][[:w:]]+[[:s:]]那个[[:s:]][[:w:]]+" 或 "通知([^\t\ n]+?)那个([^\t\n]+?)"

void searchExpression(const char *regString)

    std::string str;
    boost::regex callRegEx(regString, boost::regex_constants::icase);
    boost::cmatch im;

    while(true) 
       std::cout << "Enter String: ";
       getline(std::cin, str);
       fprintf(stderr, "str %s regstring %s\n", str.c_str(), regString);

       if(boost::regex_search(str.c_str(), im, callRegEx)) 
             int num_var = im.size() + 1;
             fprintf(stderr, "Matched num_var %d\n", num_var);
             for(int j = 0; j <= num_var; j++) 
                    fprintf(stderr, "%d) Found %s\n",j, std::string(im[j]).c_str());
             
      
      else 
          fprintf(stderr, "Not Matched\n");
      
   

我能够找到匹配的字符串，但无法提取数据。 这是输出：

input_string: Ask peter to call Regex Ask[[:s:]][[:w:]]+[[:s:]]to[[:s:]][[:w:]]+
Matched num_var 2
0) Found Ask peter to call
1) Found
2) Found

我想提取 peter 并从 Ask Peter 中调用。

【问题讨论】：

我不确定 Boost.Regex，但通常你会得到整个匹配的字符串作为结果中的索引 0 以及你在其他索引中定义的任何组。您没有定义任何组，所以这似乎是您的问题。也就是说，您使用 +1 和 >= 的索引似乎很可疑，请仔细阅读文档。

【参考方案1】：

既然你真的想要解析一个语法，你应该考虑使用 Boost 的解析器生成器。

您只需自上而下地编写整个内容：

auto sentence  = [](auto&& v, auto&& p)  
    auto verb     = lexeme [ no_case [  as_parser(v) ] ];
    auto name     = lexeme [ +graph ];
    auto particle = lexeme [ no_case [  as_parser(p) ] ];
    return confix(verb, particle) [ name ]; 
;

auto ask     = sentence("ask",     "to")   >> lexeme[+char_];
auto notify  = sentence("notify",  "that") >> lexeme[+char_];
auto message = sentence("message", "that") >> lexeme[+char_];

auto command = ask | notify | message;

这是一个 Spirit X3 语法。将lexeme 读作“保留整个单词”（不要忽略空格）。

在这里，“名称”被认为是任何与预期粒子相关的内容¹

如果你只想返回匹配的原始字符串，这就足够了：

Live On Coliru

#include <iostream>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/directive/confix.hpp>

namespace x3 = boost::spirit::x3;

namespace commands 
    namespace grammar 
        using namespace x3;

        auto sentence  = [](auto&& v, auto&& p)  
            auto verb     = lexeme [ no_case [  as_parser(v) ] ];
            auto name     = lexeme [ +graph ];
            auto particle = lexeme [ no_case [  as_parser(p) ] ];
            return confix(verb, particle) [ name ]; 
        ;

        auto ask     = sentence("ask",     "to")   >> lexeme[+char_];
        auto notify  = sentence("notify",  "that") >> lexeme[+char_];
        auto message = sentence("message", "that") >> lexeme[+char_];

        auto command = ask | notify | message;

        auto parser  = raw [ skip(space) [ command ] ];
    


int main() 
    for (std::string const input : 
            "Ask peter to call me",
            "Notify Jenna that I am going to be away",
            "Message home that I am running late",
            )
    
        std::string matched;

        if (parse(input.begin(), input.end(), commands::grammar::parser, matched))
            std::cout << "Matched: '" << matched << "'\n";
        else
            std::cout << "No match in '" << input << "'\n";
    

打印：

Matched: 'Ask peter to call me'
Matched: 'Notify Jenna that I am going to be away'
Matched: 'Message home that I am running late'

奖金

当然，您实际上是想提取相关的信息。

我会这样做。让我们解析成一个结构体：

struct Command 
    enum class Type  ask, message, notify  type;
    std::string name;
    std::string message;
;

让我们把main()写成：

commands::Command cmd;

if (parse(input.begin(), input.end(), commands::grammar::parser, cmd))
    std::cout << "Matched: " << cmd.type << "|" << cmd.name << "|" << cmd.message << "\n";
else
    std::cout << "No match in '" << input << "'\n";

Live On Coliru

#include <iostream>
#include <boost/fusion/adapted/struct.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/directive/confix.hpp>

namespace x3 = boost::spirit::x3;

namespace commands 

    struct Command 
        enum class Type  ask, message, notify  type;
        std::string name;
        std::string message;

        friend std::ostream& operator<<(std::ostream& os, Type t)  return os << static_cast<int>(t);  // TODO
    ;



BOOST_FUSION_ADAPT_STRUCT(commands::Command, type, name, message)

namespace commands 

    namespace grammar 
        using namespace x3;

        auto sentence  = [](auto type, auto&& v, auto&& p)  
            auto verb     = lexeme [ no_case [  as_parser(v) ] ];
            auto name     = lexeme [ +graph ];
            auto particle = lexeme [ no_case [  as_parser(p) ] ];
            return attr(type) >> confix(verb, particle) [ name ]; 
        ;

        using Type = Command::Type;
        auto ask     = sentence(Type::ask,     "ask",     "to")   >> lexeme[+char_];
        auto notify  = sentence(Type::notify,  "notify",  "that") >> lexeme[+char_];
        auto message = sentence(Type::message, "message", "that") >> lexeme[+char_];

        auto command // = rule<struct command, Command>  
                     = ask | notify | message;

        auto parser  = skip(space) [ command ];
    


int main() 
    for (std::string const input : 
            "Ask peter to call me",
            "Notify Jenna that I am going to be away",
            "Message home that I am running late",
            )
    
        commands::Command cmd;

        if (parse(input.begin(), input.end(), commands::grammar::parser, cmd))
            std::cout << "Matched: " << cmd.type << "|" << cmd.name << "|" << cmd.message << "\n";
        else
            std::cout << "No match in '" << input << "'\n";
    

打印

Matched: 0|peter|call me
Matched: 2|Jenna|I am going to be away
Matched: 1|home|I am running late

---

¹我不是英语语言学家，所以我不知道这是否是正确的语法术语:)

【参考方案2】：

此代码从文件“commands.txt”中读取命令字符串，搜索正则表达式并在匹配时打印部分。

#include <iostream>
#include <fstream> 
#include <string>
#include <boost/regex.hpp>

const int NumCmdParts = 4;
std::string CommandPartIds[] = "Verb", "Name", "Preposition", "Content";

int main(int argc, char *argv[])


    std::ifstream ifs;
    ifs.open ("commands.txt", std::ifstream::in);
    if (!ifs.is_open()) 
      std::cout << "Error opening file commands.txt" << std::endl;
      exit(1);
    

    std::string cmdStr;

    // Pieces of regular expression pattern
    // '(?<Verb>' : This is to name the capture group as 'Verb'
    std::string VerbPat = "(?<Verb>(Ask)|(Notify|Message))";
    std::string SeparatorPat = "\\s*";  
    std::string NamePat = "(?<Name>\\w+)";

    // Conditional expression. if (Ask) (to) else (that)
    std::string PrepositionPat = "(?<Preposition>(?(2)(to)|(that)))";
    std::string ContentPat = "(?<Content>.*)";

    // Put the pieces together to compose pattern
    std::string TotalPat = VerbPat + SeparatorPat + NamePat + SeparatorPat
                            + PrepositionPat + SeparatorPat + ContentPat;

    boost::regex actions_re(TotalPat);
    boost::smatch action_match;

    while (getline(ifs, cmdStr)) 
        bool IsMatch = boost::regex_search(cmdStr, action_match, actions_re);
        if (IsMatch)           
          for (int i=1; i <= NumCmdParts; i++)      
            std::cout << CommandPartIds[i-1] << ": " << action_match[CommandPartIds[i-1]] << "\n";
          
        
       

    ifs.close();

【讨论】：

我认为唯一使问题相关的是“通知”与“那个”一起使用，而“询问”与“到”一起使用。你的语法忽略了区别。

好收获。我会用条件表达式修复它

我喜欢命名的捕获+1