std::regex_traits<CharT>::value
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regex_traits::value
int value( CharT ch, int radix ) const;
(since C++11)
Determines the value represented by the digit ch in the numeric base radix, given the currently imbued locale. This function is called by std::regex when processing Quantifiers such as {1} or {2,5}, Backreferences such as 1円, and hexadecimal and Unicode character escapes.
[edit] Parameters
ch
-
the character that may represent a digit
radix
-
either 8, 10, or 16
[edit] Return value
The numeric value if ch indeed represents a digit in the currently imbued locale that is valid for the numeric base radix, or -1 on error.
[edit] Example
Run this code
#include <iostream> #include <locale> #include <map> #include <regex> // This custom regex traits allows japanese numerals struct jnum_traits : std::regex_traits <wchar_t> { static std::map <wchar_t, int> data; int value(wchar_t ch, int radix) const { wchar_t up = std::toupper (ch, getloc()); return data.count(up) ? data[up] : regex_traits::value(ch, radix); } }; std::map <wchar_t, int> jnum_traits::data = {{L'〇',0}, {L'一',1}, {L'二',2}, {L'三',3}, {L'四',4}, {L'五',5}, {L'六',6}, {L'七',7}, {L'八',8}, {L'九',9}, {L'A',10}, {L'B',11}, {L'C',12}, {L'D',13}, {L'E',14}, {L'F',15}}; int main() { std::locale::global (std::locale ("ja_JP.utf8")); std::wcout.sync_with_stdio(false); std::wcout.imbue(std::locale ()); std::wstring in = L"風"; if (std::regex_match (in, std::wregex (L"\\u98a8"))) std::wcout << "\\u98a8 matched " << in << '\n'; if (std::regex_match (in, std::basic_regex <wchar_t, jnum_traits>(L"\\u九八a八"))) std::wcout << L"\\u九八a八 with custom traits matched " << in << '\n'; }
Output:
\u98a8 matched 風 \u九八a八 with custom traits matched 風