{fmt} Formatting & Printing Library {fmt} Formatting & Printing Library {fmt}

#include <string_view>
#include <limits>
#include <fmt/core.h>

template <typename T>
void print_table (std::string_view label) {
    using lim = std::numeric_limits<T>;
    fmt::print("{0:-^40}\n{1}\n{0:-^40}\n","",label);
    fmt::print("lowest        {: .20}\n", lim::lowest());
    fmt::print("min           {: .20}\n", lim::min());
    fmt::print("max           {: .20}\n", lim::max());
    fmt::print("denorm_min    {: .20}\n", lim::denorm_min());
    fmt::print("epsilon       {: .20}\n", lim::epsilon());
    fmt::print("round_error   {: .20}\n", lim::round_error());
    fmt::print("min_exponent  {: }\n", lim::min_exponent);
    fmt::print("max_exponent  {: }\n", lim::max_exponent);
    fmt::print("quiet_NaN      {}\n", lim::quiet_NaN());
    fmt::print("digits        {: }\n", lim::digits);
    fmt::print("digits10      {: }\n", lim::digits10);
    fmt::print("+0            {: }\n", T(0));
    fmt::print("-0            {: }\n", T(-0.0));
} 

int main () {
    print_table<float>("FLOAT");
    print_table<double>("DOUBLE");
    print_table<long double>("LONG DOUBLE");
}

#include <fmt/chrono.h>

int main () {
auto const t = std::chrono::system_clock::now();
fmt::print("{}\n", t);
fmt::print("{:%Y-%m-%d}\n", t); 
fmt::print("-----------------------------------------------\n");
fmt::print("std. date + time          %c   {:%c}\n", t);
fmt::print("alt. date + time          %Ec  {:%Ec}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("ISO 8601 date             %F   {:%F}\n", t);
fmt::print("%m/%d/%y                  %D   {:%D}\n", t);
fmt::print("localized date            %x   {:%x}\n", t);
fmt::print("alt. date                 %Ex  {:%Ex}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("%H:%M:%S                  %T   {:%T}\n", t);
fmt::print("%H:%M                     %R   {:%R}\n", t);
fmt::print("localized 12-hour clock   %r   {:%r}\n", t);
fmt::print("localized time            %X   {:%X}\n", t);
fmt::print("alt. time                 %EX  {:%EX}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("year (last 2 digits)      %y   {:%y}\n", t);
fmt::print("year (4 digits)           %Y   {:%Y}\n", t);
fmt::print("century                   %C   {:%C}\n", t);
fmt::print("alt. localized repr.      %Ey  {:%Ey}\n", t);
fmt::print("alt. localized repr.      %EY  {:%EY}\n", t);
fmt::print("ISO 8601 week-based year  %G   {:%G}\n", t);
fmt::print("ISO 8601 week-based year  %g   {:%g}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("month                     %m   {:%m}\n", t);
fmt::print("locale-dep.               %Om  {:%Om}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("abbrev. name of month     %a   {:%a}\n", t);
fmt::print("full name of month        %A   {:%A}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("week (1st:Mon)  00-53     %W   {:%W}\n", t);
fmt::print("week (1st:Sun)  00-53     %U   {:%U}\n", t);
fmt::print("week (ISO 8601) 01-53     %V   {:%V}\n", t);
fmt::print("localized numerals        %OW  {:%OW}\n", t);
fmt::print("localized numerals        %OU  {:%OU}\n", t);
fmt::print("localized numerals        %OV  {:%OV}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("2-digit day of month      %d   {:%d}\n", t);
fmt::print("1-digit day of month      %e   {:%e}\n", t);   
fmt::print("localized numerals        %Od  {:%Od}\n", t);
fmt::print("localized numerals        %Oe  {:%Oe}\n", t);   
fmt::print("-----------------------------------------------\n");
fmt::print("weekday (Mon:1 - Sun:7)   %u   {:%u}\n", t);
fmt::print("weekday (Sun:0 - Sat:6)   %w   {:%w}\n", t);
fmt::print("local.  (Mon:1 - Sun:7)   %Ou  {:%Ou}\n", t);
fmt::print("local.  (Sun:0 - Sat:6)   %Ow  {:%Ow}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("abbrev. name of day       %b   {:%b}\n", t);
fmt::print("full name of day          %B   {:%B}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("day of year               %j   {:%j}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("hours (24-based)          %H   {:%H}\n", t);
fmt::print("hours (12-based)          %I   {:%I}\n", t);
fmt::print("localized numerals        %OH  {:%OH}\n", t);
fmt::print("localized numerals        %OI  {:%OI}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("minutes                   %M   {:%M}\n", t);
fmt::print("localized numerals        %OM  {:%OM}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("seconds                   %S   {:%S}\n", t);
fmt::print("localized numerals        %OS  {:%OS}\n", t);
fmt::print("-----------------------------------------------\n");
fmt::print("offset from UTC           %z   {:%z}\n", t);
fmt::print("time zone abbrev.         %Z   {:%Z}\n", t);
}

#include <iostream>
#include <string>

#include <fmt/ostream.h>

struct point2d {
  int x;
  int y;

  point2d(int x_, int y_): x(x_), y(y_) {}

  friend std::ostream&   operator << (std::ostream& os, point2d const& p)   {
    return os << '(' << p.x << ',' << p.y << ')';
  }
};

int main () {
std::string s = fmt::format("Position is {}", point2d{7,9});
// s = "Position is (7,9)"

std::cout << s << '\n';

fmt::print("{}\n", s);
}

#include <fmt/format.h>

enum class color {red, green, blue};

template <>
struct fmt::formatter<color> :   formatter<string_view>
{
  // use inherited 'formatter<string_view>::parse'…

  // … and only implement 'format':
  template <typename FmtContext>
  auto format (color c, FmtContext& ctx) {
    string_view name = "unknown";
    switch (c) {
      case color::red:         name = "red"; break;
      case color::green:       name = "green"; break;
      case color::blue:        name = "blue"; break;
    }
    return formatter<string_view>::format(name, ctx);
  }
};

int main () {
  fmt::print("|{:>10}|\n", color::blue);
}

#include <vector>
#include <fmt/ranges.h>

class IntList {
  std::vector<int> v_;
public:
  explicit 
  IntList (std::initializer_list<int> il): v_{il} {}
  [[nodiscard]] auto begin () const noexcept { return v_.begin(); }
  [[nodiscard]] auto end ()   const noexcept { return v_.end(); }
};

int main () {
  IntList l {4,8,15,16,23,42};
  fmt::print("numbers: {}\n", l);
}

#include <fmt/ranges.h>

class Point4 {
  double v_ [4];
public:
  explicit 
  Point4 (double x, double y, double z, double w): v_{x,y,z,w} {}
  [[nodiscard]] double x () const noexcept { return v_[0]; }
  [[nodiscard]] double y () const noexcept { return v_[1]; }
  [[nodiscard]] double z () const noexcept { return v_[2]; }
  [[nodiscard]] double w () const noexcept { return v_[3]; }
  [[nodiscard]] double const* begin () const noexcept { return v_; }
  [[nodiscard]] double const* end ()   const noexcept { return v_+4; }
};

int main () {
  Point4 v {4.7,2.,1.,3.2};
  fmt::print("point: {}\n", v);
}

#include <fmt/format.h>

int main () {
fmt::vprint("{}\n", fmt::make_format_args(47));
fmt::vprint("{} of {}\n", fmt::make_format_args("seven", 9));
}

#include <fmt/format.h>

void vcomment (fmt::string_view format, fmt::format_args args) {
  fmt::print("<-- ");
  fmt::vprint(format, args);
  fmt::print(" -->\n");
}

template <typename Str, typename... Args>
void comment (Str const& format, Args&&... args) {
  vcomment(format, fmt::make_args_checked<Args...>(format, args...));
}

int main () {
  double const d = 12.345;
  comment("{:e} and {}", d, 47);
}