std::regex_traits<CharT>::value
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Revision as of 10:25, 21 October 2023 by Andreas Krug (Talk | contribs)
| 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 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() {