Question

我的代码应执行以下操作：
输入：（x + y）=>（x * y）
输出：（x + y）
regexp运作良好，我在regexp101.com网站上对其进行了测试如果我从regexp_match（）中删除match参数，则代码有效。
但是它不返回正则表达式结果。运行此命令时出现此错误：

> g++ -std=c++11 main.cpp

错误

main.cpp:14:9: error: no matching function for call to 'regex_match'
    if (regex_match(formula,match, firstBrace)){
        ^~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/regex:6038:1: note: 
      candidate template ignored: deduced conflicting types for parameter '_BidirectionalIterator'
      ('std::__1::basic_string<char>' vs. 'std::__1::match_results<const char *,
      std::__1::allocator<std::__1::sub_match<const char *> > >')
regex_match(_BidirectionalIterator __first, _BidirectionalIterator __last,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/regex:6049:1: note: 
      candidate template ignored: could not match 'const _CharT *' against 'std::__1::string' (aka
      'basic_string<char, char_traits<char>, allocator<char> >')
regex_match(const _CharT* __str, match_results<const _CharT*, _Allocator>& __m,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/regex:6059:1: note: 
      candidate template ignored: deduced type 'match_results<typename basic_string<char,
      char_traits<char>, allocator<char> >::const_iterator, [...]>' of 2nd parameter does not match
      adjusted type 'match_results<const char *, [...]>' of argument [with _ST =
      std::__1::char_traits<char>, _SA = std::__1::allocator<char>, _Allocator =
      std::__1::allocator<std::__1::sub_match<const char *> >, _CharT = char, _Traits =
      std::__1::regex_traits<char>]
regex_match(const basic_string<_CharT, _ST, _SA>& __s,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/regex:6080:1: note: 
      candidate template ignored: could not match 'const _CharT *' against 'std::__1::string' (aka
      'basic_string<char, char_traits<char>, allocator<char> >')
regex_match(const _CharT* __str, const basic_regex<_CharT, _Traits>& __e,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/regex:6089:1: note: 
      candidate template ignored: could not match 'basic_regex' against 'match_results'
regex_match(const basic_string<_CharT, _ST, _SA>& __s,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/regex:5366:5: note: 
      candidate function template not viable: requires at least 4 arguments, but 3 were provided
    regex_match(_Bp, _Bp, match_results<_Bp, _Ap>&, const basic_regex<_Cp, _Tp>&,
    ^
1 error generated.


#include <iostream>
#include <string>
#include <regex>
using namespace std;

int main() {
    string formula;

    cout << "Write down a formula" << endl;
    cin >> formula;
    cmatch match;

    regex firstBrace("(\\()(\\w\\+)+(.\\))\\s?");
    if (regex_match(formula,match, firstBrace)){
        cout << "String 'a' matches regular expression 'b' \n";
        cmatch mcopy (match);  // copy constructor
        for (unsigned i=0; i<mcopy.size(); ++i)
            cout << "match " << i << ": " << mcopy[i] << endl;
    }

    return 0;
}

如何从正则表达式中得到结果？

Answer 1

您当前的代码无法编译，因为目标类型与 match 结果类型不匹配。如果您通过string作为输入，则匹配的结果将存储在smatch中。输入为const char*时，结果存储在cmatch中。

您必须将cmatch个事件替换为smatch。

如何从regexp_match（）获得结果

1 个答案: