commonLength

["Nordlöw" via Digitalmars-d-learn]

On Thursday, 15 January 2015 at 13:13:57 UTC, Nordlöw wrote:
> I just discovered that zip has StoppingPolicy so why does
>
> auto commonPrefixLength(R...)(R ranges) if (ranges.length == 2)
> {
>     import std.range: zip;
>     return zip!((a, b) => a[0] != b[1])(ranges);
> }

I did a silly mistake. The correct version is

auto commonPrefixLength(S, T)(S a, T b)
{
     import std.range: zip, StoppingPolicy;
     import std.algorithm: countUntil, count;
     const hit = zip(a, b).countUntil!(ab => ab[0] != ab[1]);
     return hit == -1 ? zip(a, b).count : hit;
}

This however needs to process zip(a, b) how do I avoid the extra 
count?

If countUntil returned zip(a, b).count upon failure I would have 
been done...