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 operations.
| new_width | - | new field width setting |
The field width before the call to the function.
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 operator>> overload page individually.
#include <array>
#include <tuple>
#include <ctime>
#include <string>
#include <iostream>
#include <sstream>
#include <iomanip>
int main()
{
auto str_time = [](int year, int mon, int day)
{
constexpr std::array<const char*, 7> week_day{ {
"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
} };
std::tm tm{};
tm.tm_year = year - 1900;
tm.tm_mon = mon - 1;
tm.tm_mday = day;
day += mon < 3 ? year-- : year - 2;
tm.tm_wday = (23 * mon / 9 + day + 4 + year / 4 - year / 100 + year / 400) % 7;
std::ostringstream out;
out << week_day[tm.tm_wday] << ", " << std::put_time(&tm, "%B %d, %Y");
return out.str();
};
constexpr int column_size = 4;
using table_t = std::array<std::string, column_size>;
table_t headers{ { "Name", "Birthdate", "Death date", "Language Created" } };
std::array<table_t, 5> data{ {
{ { "Dennis MacAlistair Ritchie", str_time(1941, 9, 9), str_time(2011, 10, 12), "C" } },
{ { "Bjarne Stroustrup", str_time(1950, 12, 30), "", "C++" } },
{ { "Anders Hejlsberg", str_time(1960, 12, 2), "", "C#" } },
{ { "Guido van Rossum", str_time(1956, 1, 31), "", "Python" } },
{ { "Brendan Eich", str_time(1961, 7, 4), "", "Javascript" } }
} };
constexpr int name_wid = 30;
constexpr int birth_wid = 30;
constexpr int death_wid = 30;
constexpr int lang_wid = 18;
auto print_line = [](table_t const &tbl)
{
auto const &[Name, Birthdate, DeathDate, LanguageCreated] = tbl;
std::cout.width(name_wid);
std::cout << ("| " + Name) << '|';
std::cout.width(birth_wid);
std::cout << (' ' + Birthdate) << '|';
std::cout.width(death_wid);
std::cout << (' ' + DeathDate) << '|';
std::cout.width(lang_wid);
std::cout << (' ' + LanguageCreated) << '|';
std::cout << '\n';
};
constexpr int total_wid = name_wid + birth_wid + death_wid + lang_wid + column_size;
auto print_break = []
{
std::cout.width(total_wid);
std::cout.fill('-');
std::cout << '-' << std::endl;
std::cout.fill(' ');
};
std::cout.setf(std::ios::left, std::ios::adjustfield);
print_break();
print_line(headers);
print_break();
for (auto const &entry : data)
print_line(entry);
print_break();
}Output:
---------------------------------------------------------------------------------------------------------------- | Name | Birthdate | Death date | Language Created | ---------------------------------------------------------------------------------------------------------------- | Dennis MacAlistair Ritchie | Tuesday, September 09, 1941 | Wednesday, October 12, 2011 | C | | Bjarne Stroustrup | Saturday, December 30, 1950 | | C++ | | Anders Hejlsberg | Friday, December 02, 1960 | | C# | | Guido van Rossum | Tuesday, January 31, 1956 | | Python | | Brendan Eich | Tuesday, July 04, 1961 | | Javascript | ----------------------------------------------------------------------------------------------------------------
| manages decimal precision of floating point operations (public member function) |
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