C ++ Boost正则表达式替换为条件 [英] C++ boost regex replace with conditions

问题描述

我目前正在用C ++写一个日期格式库.例如.该库采用格式字符串，例如: dddd，mmmm d，dddd yyyy ，并产生结果 2016年12月26日星期二，星期二给定年份:2016，月份:12，日期:26( dddd 代表工作日， d 代表数字中的日期， mmmm 代表月份， yyyy 代表年份.

我想通过使用 boost :: regex_replace 来实现这一点.

I am currently writing a date formatting library in C++. For example. the library takes in a formatting string such as: dddd, mmmm d, dddd yyyy and produces a result Tuesday, December 26, Tuesday 2016 given year: 2016, month: 12, date: 26 (dddd stands for weekday, d stands for date in number, mmmm stands for month, yyyy stands for year).

I would like to achieve this by using boost::regex_replace.

在 javascript 中，我可以通过以下操作轻松实现此目标:

In javascript I can easily achieve this by doing:

var pattern = 'dddd, mmmm d, yyyy';
pattern.replace(/(dddd)|(d)|(mmmm)|(yyyy)/gi, function (dddd, d, mmmm, yyyy){
    if (dddd) {
        return 'Tuesday';
    }

    if (d) {
        return '26'
    }

    if (mmmm) {
        return 'December';
    }

    if (yyyy) {
       return '2016';
    }
    return '';
}

C ++

---

boost::regex regex1("(dddd)");
boost::regex regex2("(d)");
boost::regex regex3("(mmmm)");
boost::regex regex4("(yyyy)");
boost::smatch match;

// dddd
if (boost::regex_search(pattern, match, regex1))
{
    pattern = boost::regex_replace(pattern, regex1, "Tuesday");
}

// d
if (boost::regex_search(pattern, match, regex2))
{
    pattern = boost::regex_replace(pattern, regex2, "26");
}

// mmmm
if (boost::regex_search(pattern, match, regex3))
{
        pattern = boost::regex_replace(pattern, regex3, "December");
}

// yyyy
if (boost::regex_search(pattern, match, regex4))
{
    pattern = boost::regex_replace(pattern, regex4, "2016");
}

但是，这给了我"Tues26ay，December 26，Tues26ay 2016" 的结果.原因是:只要我将模式 dddd 替换为 Tuesday ， Tuesday 内的 d 就会成为目标regex2 的模式，导致将其替换为 26 .

我不确定如何解决此问题，或者我认为解决该问题的C ++方法不正确.是否有可能在C ++ boost :: regex中提供类似于Javascript的东西?

任何帮助将不胜感激！

However, that gives me a result of "Tues26ay, December 26, Tues26ay 2016". The reason is that: as soon as I replace pattern dddd with Tuesday, the d inside Tuesday becomes a target pattern for regex2 causing it to be replaced with 26.

I am not sure how to fix this problem or I think my C++ way for solving this problem is not correct. Is it possible to have something similar as Javascript in C++ boost::regex?

Any help would be appreciated!

推荐答案

我不知道您为什么不按字面意义进行一对一翻译:

I don't know why you didn't literally 1-on-1 translate:

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

int main() {
    std::string pattern = "dddd, mmmm d, yyyy";
    pattern = boost::regex_replace(pattern, boost::regex("(dddd)|(d)|(mmmm)|(yyyy)"), [](auto& match)->std::string{
        if (match.str() == "dddd")
            return "Tuesday";

        if (match.str() == "d")
            return "26";

        if (match.str() == "mmmm")
            return "December";

        if (match.str() == "yyyy")
            return "2016";

        return "";
    });

    std::cout << "Result: " << pattern << "\n";
}

打印

Result: Tuesday, December 26, 2016

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