Coding Challenges - Dlang or Generic

[Salih Dincer]

On Tuesday, 17 January 2023 at 21:50:06 UTC, matheus wrote:
> Have you compared the timings between this way (With ranges) 
> and a normal way (Without ranges)?

Of course it is possible to speed it up.  However, even as it is, 
it is enough to see the power of intervals.  I would argue that 
you'll get fast results even with DMD Compiler!

```d
import std.stdio;
import std.datetime.date;

void main()
{
   import std.datetime.stopwatch : benchmark, StopWatch;
   auto sw = StopWatch();

#line 1
   sw.start();

   enum xTest = 1200;
   auto title = enumToStr!DayOfWeek(2);

   auto date = Date(2023, 12, 1);
   auto range = MyCalendar(date);
   for(size_t test; test < xTest; range.popFront, ++test)
   {
     range.writeln;             // month and year
     title.writefln!"%-(%s %)"; // days of week
     range.front.writeln;       // formatted days
   }
   sw.stop();
   writeln(sw.peek.total!"usecs");
}

struct MyCalendar
{
   import std.array  : appender, replicate;
   import std.format : format, formattedWrite;
   import std.string : capitalize;

   Date date;
   enum empty = false;

   string front()
   {
     auto res = appender!string;
     int day, dow = date.dayOfWeek;
     // skip days:
     res.formattedWrite("%s", " ".replicate(dow * 3));

     for(day = 1; day <= date.daysInMonth; ++day)
     {
       res.formattedWrite("%2s ", day);
       if(++dow % 7 == 0) res.put("\n");
     }
     if(dow % 7) res.put("\n");
     return res.data;
   }

   void popFront()
   {
     date.roll!"months"(1);
   }

   string toString() const
   {
     const currentYear = date.year;   // Current Year
     const currentMonth = date.month; // Name of the month
     const monthAndYear = format("%s/%s:",
                             currentMonth,
                             currentYear);
     return capitalize(monthAndYear);
   }
}

auto enumToStr(E)(size_t len = 0)
{
   import std.conv : to;
   string[] result;
   for(E x = E.min; x <= E.max; x++)
   {
     result ~= len ? x.to!string[0..len]
                   : x.to!string;
   }
   return result;
}
```
SDB at 79