| Localization library | |||||||||||||||||||||||||
| Regular expressions library(C++11) | |||||||||||||||||||||||||
| Formatting library(C++20) | |||||||||||||||||||||||||
| Null-terminated sequence utilities | |||||||||||||||||||||||||
| Byte strings | |||||||||||||||||||||||||
| Multibyte strings | |||||||||||||||||||||||||
| Wide strings | |||||||||||||||||||||||||
| Primitive numeric conversions | |||||||||||||||||||||||||
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| Text encoding identifications | |||||||||||||||||||||||||
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| Member functions | ||||
collate::transformcollate::do_transform | ||||
Defined in header <locale> | ||
public: string_type transform(const CharT* low,const CharT* high)const; | (1) | |
protected: virtual string_type do_transform(const CharT* low,const CharT* high)const; | (2) | |
do_transform of the most derived class.[low, high) to a string that, compared lexicographically (e.g. withoperator< for strings) with the result of callingtransform() on another string, produces the same result as callingdo_compare() on the same two strings.Contents |
| low | - | pointer to the first character in the sequence to transform |
| high | - | one past the end pointer for the sequence to transform |
The string transformed so that lexicographic comparison of the transformed strings may be used instead of collating of the originals. In the "C" locale, the returned string is the exact copy of[low, high). In other locales, the contents of the returned string are implementation-defined, and the size may be considerably longer.
In addition to the use in collation, the implementation-specific format of the transformed string is known tostd::regex_traits<>::transform_primary, which is able to extract the equivalence class information.
#include <iomanip>#include <iostream>#include <locale> int main(){std::locale::global(std::locale("sv_SE.utf8"));auto& f=std::use_facet<std::collate<wchar_t>>(std::locale()); std::wstring in1= L"\u00e4ngel";std::wstring in2= L"\u00e5r"; std::wstring out1= f.transform(&in1[0],&in1[0]+ in1.size());std::wstring out2= f.transform(&in2[0],&in2[0]+ in2.size()); std::wcout<<"In the Swedish locale: ";if(out1< out2)std::wcout<< in1<<" before "<< in2<<'\n';elsestd::wcout<< in2<<" before "<< in1<<'\n'; std::wcout<<"In lexicographic comparison: ";if(in1< in2)std::wcout<< in1<<" before "<< in2<<'\n';elsestd::wcout<< in2<<" before "<< in1<<'\n';}
Output:
In the Swedish locale: år before ängelIn lexicographic comparison: ängel before år
transform a string so thatstrcmp would produce the same result asstrcoll(function)[edit] | |
transform a wide string so thatwcscmp would produce the same result aswcscoll(function)[edit] |
