C++中的regex_error

regex_error存在于标题“ regex”内部和类regex_error中； 。它有助于我们了解程序执行过程中引发的错误，它在正则表达式库中定义异常对象的类型，还描述了basic_regex对象的构造或使用中的错误。构造用于保留值错误的对象起着重要作用，该对象继承自std ::异常

下面列出了十三种错误：

FLAGS	ERRORS
error_collate	This expressions have element names having invalid collation.
error_ctype	This expressions have an invalid character class name.
error_stack	If there is not enough memory to determine whether the regular expressions can match a give characters sequence.
error_space	This occurs to convert into finite state machine when memory is insufficient.
error_badrepeat	This contains a repeat specifier ( *?+{) that was not preceded by a valid regular expression.
error_complexity	The complexity of an attempted match against a regular expression exceeded a pre-set level
error_range	when contains an invalid character range.
error_badbrace	The expression contains invalid range between braces { and }.
error_brace	The expression contains mismatched braces { and }.
error_paren	The expression contains mismatched parentheses ( and ).
error_brack	The expression contains mismatched brackets ([ and ]).
error_backref	The expression excepts invalid back reference.
error_escape	The expression does not allows any invalid escaped character, or a trailing escape.
error_escape	The expression does not allows any invalid escaped character, or a trailing escape.

下面是一个演示正则表达式错误的简单程序。

程序1：

// Program to demonstrate the error
int main()
{
#include 
#include 
  
    int main()
    {
        try {
            std::regex re("[1-9][0");
        }
  
        catch (const std::regex_error& err) {
            std::cout << "There was a regex_error caughted: " 
            << err.what() << '\n';
            if (err.code() == std::regex_constants::error_brack) {
                std::cout << "The code gives an error_brack\n";
            }
        }
    }
    return 0;
}

输出：

regex_error caught: Unexpected character in bracket expression.
        The code gives an error_brack

程式2：

// Program to demonstrate no error
#include 
#include 
  
int main()
{
    try {
        std::regex re("[A-Z][bcd] ");
    }
  
    catch (const std::regex_error& er) {
        std::cout << "regex_error caught: "
        << er.what() << '\n';
        if (er.code() == std::regex_constants::error_brack) {
            std::cout << "The code was this is the error error_brack\n";
        }
    }
}

注意：因为没有错误，所以没有输出。

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