What is the 'Result' type even for?

[Ruby The Roobster]

Take this example:

```d
import std;
void main()
{
     auto c = "a|b|c|d|e".splitter('|');
     c.writeln;
     string[] e = ["a", "b", "c", "d", "e"];
     assert(c.equal(e));
     typeof(c).stringof.writeln;
}
```

The program prints:

["a", "b", "c", "d", "e"]
Result

What is the purpose of this 'Result' type?  To serve as a generic 
range?  Because, it seems to only cause problems.  For example, 
you cannot assign or cast the result type into a range, even when 
the type has the same inherent function:

```d
string[] c = "a|b|c|d|e".splitter('|'); // fails
string[] d = cast(string[])"a|b|c|d|e".splitter('|'); // also 
fails
```

And if you need to perform a set operation?

```d
c[] ~= "lolno"; // fails, as [] isn't defined for Result.
```

Then what is the point of this type, if not to just make things 
difficult?  It cannot be casted, and vector operations cannot be 
performed, and it seems to just serve as an unnecessary 
generalization.