C++ Locale Library - narrow

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Description

It is used in narrow characters and internally, this function simply calls the virtual protected member do_narrow, which does the above by default in both the generic template and the char specialization (ctype<char>).

Declaration

Following is the declaration for std::ctype::narrow.

C++98

	
char narrow (char_type c, char dfault) const;

C++11

char narrow (char_type c, char dfault) const;

Parameters

• c − It is a char type.

• low,high − It is a pointer to the beginning and end of the sequence of characters.

• to − It is a pointer to a range of elements of the facet's character type.

• dfault − It is a default character value.

Return Value

It returns the transformation of c.

Exceptions

If an exception is thrown, there are no changes in the facet object, although characters in the range may have been affected.

Data races

The object, and the elements in the range [low,high), are accessed.

Example

In below example explains about std::ctype::narrow.

#include <iostream>
#include <locale>
#include <string>

int main () {
   std::locale loc;
   std::wstring yourname;

   std::cout << "Please enter your a word: ";
   std::getline (std::wcin,yourname);
   std::wstring::size_type length = yourname.length();

   std::cout << "The first (narrow) character in your word is: ";
   std::cout << std::use_facet< std::ctype<wchar_t> >(loc).narrow ( yourname[0], '?' );
   std::cout << '\n';

   std::cout << "The narrow transformation of your word is: ";
   char * pc = new char [length+1];
   std::use_facet< std::ctype<wchar_t> >(loc).narrow ( yourname.c_str(), 
      yourname.c_str()+length+1, '?', pc);
   std::cout << pc << '\n';

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Please enter your a word: sai
The first (narrow) character in your word is: s
The narrow transformation of your word is: sai