std::regex_traits<CharT>::value
From cppreference.com
< cpp | regex | regex traits
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, 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 numeralsstruct jnum_traits :std::regex_traits<wchar_t>{staticstd::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
