What is the 'Result' type even for?

[Ruby The Roobster]

On Friday, 20 January 2023 at 03:11:33 UTC, Ruby The Roobster 
wrote:
> 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.

Furthermore, it can also be confirmed that each member of c is a 
string, further solidifying my opinion of 'Result' as just being 
a generic range template, that cannot be casted to an array of 
the original type.