range simple toy problem

[ag0aep6g]

On 06/01/2018 07:00 PM, Xiaoxi wrote:
> import std.range;
> import std.algorithm;
> import std.string;
> import std.stdio;
> 
> void main()
> {
>    auto s = "1 2 3 4 5 6 7 8 9";
>    auto iter = s.split(" ").drop(2);
> 
>    // How to find the unconsumed/not-split part of s here?
>    // i.e. "3 4 5 6 7 8 9" NOT ["3", "4", "5", "6", "7", "8", "9"]
>    // s[??? .. $] <- what goes here?
> }

This prints "3 4 5 6 7 8 9":

----
import std.range;
import std.algorithm;
import std.stdio;

void main()
{
    auto s = "1 2 3 4 5 6 7 8 9";
    auto iter = refRange(&s).splitter!(c => c == ' ').drop(2);
    writeln(s); /* "3 4 5 6 7 8 9" */
}
----

Arguably, `.splitter(' ')` should work as well, but it doesn't.

Warning: Large parts of Phobos, including `splitter`, have problems 
handling a `RefRange`. So this might break down when you take it beyond 
the toy stage.
https://issues.dlang.org/show_bug.cgi?id=18657

> split is just an example, it's a generic question if you chain multiple 
> lazy functions and then consume a part of the data...

Nitpick: `split` is not lazy. `splitter` is.

> how do you know 
> how to slice the original buffer to point to the unconsumed data? 

In my opinion, `refRange` should fit the bill here. But:

1) It's not always clear from the documentation how much a lazy function 
actually pops. It might pop more than you expect, or less.
2) As mentioned, `refRange` has compatibility issues with other parts of 
Phobos.