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std::ios_base::width(3)        C++ Standard Libary	 std::ios_base::width(3)

NAME
     std::ios_base::width - std::ios_base::width

Synopsis
	streamsize width() const;		  (1)
	streamsize width( streamsize new_width ); (2)

	Manages  the  minimum number of characters to generate on certain output
     operations
	and the maximum number of characters to generate on certain input opera-
     tions.

	1) Returns the current field width.
	2) Sets the field width to the given one.  Returns  the  previous  field
     width.

Parameters
	new_width - new field width setting

Return value
	The field width before the call to the function.

Notes
	Some  I/O  functions call width(0) before returning, see std::setw (this
     results in
	this field having effect on the next I/O function only, and not  on  any
     subsequent
	I/O).

	The exact effects this modifier has on the input and output vary between
     the
	individual I/O functions and are described at each operator<< and opera-
     tor>>
	overload page individually.

Example
     // Run this code

      #include <algorithm>
      #include <array>
      #include <iomanip>
      #include <iostream>
      #include <span>
      #include <string_view>
      using namespace std::string_view_literals;

      constexpr std::array table_header =
      {
	  "Language"sv, "Author"sv, "Birthdate"sv, "RIP date"sv
      };

      using row_t = std::array<std::string_view, table_header.size()>;
      using widths_t = std::array<std::size_t, table_header.size()>;

      constexpr std::array table_body = std::to_array<row_t>
      ({
	  {"C", "Dennis Ritchie", "1941-09-09", "2011-10-12"},
	  {"C++", "Bjarne Stroustrup", "1950-12-30"},
	  {"C#", "Anders Hejlsberg", "1960-12-02"},
	  {"Python", "Guido van Rossum", "1956-01-31"},
	  {"Javascript", "Brendan Eich", "1961-07-04"}
      });

      constexpr widths_t calculate_column_widths(std::span<const row_t> table)
      {
	  widths_t widths{};
	  for (const row_t& row : table)
	      for (size_t i = 0; i != row.size(); ++i)
		  widths[i] = std::max(widths[i], row[i].size());
	  return widths;
      }

      void print_row(const row_t& row, const widths_t& widths)
      {
	  std::cout << '|';
	  for (size_t i = 0; i != row.size(); ++i)
	  {
	      std::cout << ' ';
	      std::cout.width(widths[i]);
	      std::cout << row[i] << " |";
	  }
	  std::cout << '\n';
      };

      void print_break(const widths_t& widths)
      {
	  const std::size_t margin = 1;
	  std::cout.put('+').fill('-');
	  for (std::size_t w : widths)
	  {
	      std::cout.width(w + margin * 2);
	      std::cout << '-' << '+';
	  }
	  std::cout.put('\n').fill(' ');
      };

      int main()
      {
	  constexpr widths_t widths = calculate_column_widths(table_body);

	  std::cout.setf(std::ios::left, std::ios::adjustfield);
	  print_break(widths);
	  print_row(table_header, widths);
	  print_break(widths);
	  for (const row_t& row : table_body)
	      print_row(row, widths);
	  print_break(widths);
      }

Output:
      +------------+-------------------+------------+------------+
      | Language   | Author	       | Birthdate  | RIP date	 |
      +------------+-------------------+------------+------------+
      | C	   | Dennis Ritchie    | 1941-09-09 | 2011-10-12 |
      | C++	   | Bjarne Stroustrup | 1950-12-30 |		 |
      | C#	   | Anders Hejlsberg  | 1960-12-02 |		 |
      | Python	   | Guido van Rossum  | 1956-01-31 |		 |
      | Javascript | Brendan Eich      | 1961-07-04 |		 |
      +------------+-------------------+------------+------------+

See also
	precision manages decimal precision of floating point operations
		  (public member function)
	setw	  changes the width of the next input/output field
		  (function)

http://cppreference.com 	   2024.06.10		 std::ios_base::width(3)
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