c++ - 使用正则表达式进行输入验证

Question

我知道以下不是最有效的实现(毕竟我可以在 main() 中运行 regex_match() )但它应该仍然有效，至少从我有限的理解来看是这样。

我正在尝试在 C++11 中使用来验证 dicerolls 的一些输入。我使用 expresso 来构建正则表达式，它在 expresso 中验证它就好了。为什么它会在此代码中失败？

#include <iostream>
#include <string>
#include <regex>

bool regexValidate (string expr, string teststring) 
{
    regex ex(expr);
    if (regex_match(teststring,ex)) {
        return true;
        cout << "true";
    } else if (regex_match (teststring,regex("^\s*\d*d\d*\s*$"))) {
        return true;
        cout << "true";
    }
    return false;
}

int main() 
{
    char    choice;             // menu option selected by user
    bool    isExit = false;     // Is the user ready to exit?         

    // test code
    string  diceexpr = "^\s*\d{1,}d\d{1,}\s*$";
    string  teststr = "10d10";
    string  teststr1 = "1d10";
    string  teststr2 = " 10d10 ";

    cout << teststr << " is ";
    if (regexValidate(diceexpr,teststr)) {
        cout << " valid!" << endl;
    } else {
        cout << " invalid!" << endl;
    }
    cout << teststr1 << " is ";
    if (regexValidate(diceexpr,teststr1)) {
        cout << " valid!" << endl;
    } else {
        cout << " invalid!" << endl;
    }
    cout << teststr2 << " is ";
    if (regexValidate(diceexpr,teststr2)) {
        cout << " valid!" << endl;
    } else {
        cout << " invalid!" << endl;
    }
    return 0;
}

示例输出:

10d10 is  invalid!
1d10 is  invalid!
 10d10  is  invalid!

RUN SUCCESSFUL (total time: 291ms)

更新

更正了我的代码并将其更改为将 boost 库用于正则表达式。

#include <iostream>
#include <string>
#include <boost/regex.hpp>
using namespace std;

bool regexValidate (string expr, string teststring) 
{
    boost::regex ex(expr);
    if ( boost::regex_match (teststring,ex) ) {
        cout << "true";
        return true;
    //} else if (regex_match (teststring,regex("^\s*\d*d\d*\s*$"))) {
    //    cout << "true";
    //    return true;
    }
    return false;
}

int main()
{
    string  diceexpr = "^\\s*\\d{1,}d\\d{1,}\\s*$";
    string  teststr = "10d10";
    string  teststr1 = "1d10";
    string  teststr2 = " 10d10 ";

    cout << teststr << " is ";
    if (regexValidate(diceexpr,teststr)) {
        cout << " valid!" << endl;
    } else {
        cout << " invalid!" << endl;
    }
    cout << teststr1 << " is ";
    if (regexValidate(diceexpr,teststr1)) {
        cout << " valid!" << endl;
    } else {
        cout << " invalid!" << endl;
    }
    cout << teststr2 << " is ";
    if (regexValidate(diceexpr,teststr2)) {
        cout << " valid!" << endl;
    } else {
        cout << " invalid!" << endl;
    }
    return 0;
}

给定以下输出:

terminate called after throwing an instance of 'std::regex_error'
  what():  regex_error

RUN FAILED (exit value 1, total time: 1s)

Answer 1

string diceexpr = "^\s*\d{1,}d\d{1,}\s*$";

这并不像您想象的那样。在字符串文字中，"\s" 与 "s" 相同(您应该会看到有关无法识别的转义序列的编译器警告)，而 "\\s" 代表两个字符，反斜杠和's'。

将所有反斜杠加倍，或者为您的正则表达式使用原始字符串文字，如

string  diceexpr = R"(^\s*\d{1,}d\d{1,}\s*$)";