How Can I Change the Delimiter for `cin` Input in C ?

Modifying the Delimiter for 'cin' Input in C

When working with input streams in C , it's common to use 'cin' to read user input. By default, 'cin' treats whitespace characters as delimiters, separating words or tokens. What if you need to use a different delimiter?

While the C Standard Library API doesn't explicitly provide a method to change the delimiter for 'cin,' it is possible to achieve this using the 'std::ios_base::imbue' function.

'std::ios_base::imbue' allows you to add a custom 'ctype' facet to the input stream. Ctype facets define the character classification behavior for a given locale.

Here's an example that demonstrates how to change the delimiter to the colon (':') character:

#include <locale>
#include <iostream>

struct colon_is_space : std::ctype<char> {
  colon_is_space() : std::ctype<char>(get_table()) {}
  static mask const* get_table()
  {
    static mask rc[table_size];
    rc[':'] = std::ctype_base::space;
    rc['\n'] = std::ctype_base::space;
    return &amp;rc[0];
  }
};

int main() {
  using std::string;
  using std::cin;
  using std::locale;

  cin.imbue(locale(cin.getloc(), new colon_is_space));

  string word;
  while(cin >> word) {
    std::cout << word << "\n";
  }
}

In this example, a custom 'ctype' facet, 'colon_is_space,' is created. This facet classifies the colon (':') and newline ('n') characters as spaces.

By imbuing the input stream with a locale using this custom facet, we effectively change the delimiter for 'cin' to the colon. As a result, when reading input using the extraction operator (>>), it will treat the colon as a separator.

This technique can be used to handle input formats that use non-whitespace characters as delimiters.

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