number ranges

[Salih Dincer]

On Tuesday, 18 January 2022 at 23:13:14 UTC, Ali Çehreli wrote:
>
> But I like the following one better because
> it is fast and I think it works correctly.

Is it okay to swap places instead of throwing an error? Let's 
also implement BidirectionalRange, if okay. This great struct 
will now run 4x4 like a Jeep. 😀

Moreover, the iota doesn't even care if define char type. And no 
throwing an error.

The real question to ask is:

"Does it reverse the result
in case ```a > b``` like we
did with foreach_reverse()"

Salih

```d
import std;

struct InclusiveRange(T) {
   T front, last;

   this(U)(in U front, in U last) {
     this.front = front;
     this.last = last;

     if(empty) toogleFrontLast();
   }

   bool empty() {
     return front > last;
   }

   void popFront() {
     if(!empty) ++front;
   }

   T back() {
     return last;
   }

   void popBack() {
     if(!empty) --last;
   }

   void toogleFrontLast() {
     auto temp = this.last;
     this.last = this.front;
     this.front = temp;
   }
}

auto inclusiveRange(T)(T first, T last) {
   return InclusiveRange!T(first, last);
}

     enum a = 8; // ASCII 80: P
     enum b = 7; // ASCII 70: F

     alias type = char;
     alias test = inclusiveRange;

void main() {
   string str; // for tests...
   auto io = iota!type(a * 10, b * 10);
        io.writeln("\n", typeof(io).stringof, "\n");

   str = to!string(io);
   assert(str == "[]"); // OMG, why?

   auto ir = test!type(a * 10, b * 10);
        ir.writeln("\n", typeof(ir).stringof, "\n");

   str = to!string(ir);
   assert(str == "FGHIJKLMNOP"); // Ok

   foreach_reverse(c; ir) str ~= c;
   assert(str == "FGHIJKLMNOPPONMLKJIHGF"); // Ok
}
```