I have array of structs sorted by specific field. How can I perform binary search using this field as a key?

Currently I ended up with this, but it gives error:

struct S
{
    int i;
    string s;
}

import std.range;

void main(string [] args)
{
    S[] structs = [{1,"hello"}, {2,"world"}, {3, "!"}]; //sorted by i

    auto sortedRange = assumeSorted!(function bool(ref const S item, int needle) {
        return item.i < needle;
    })(structs);

    sortedRange.trisect(2); //compilation error
}

On Sunday, 5 April 2015 at 23:06:27 UTC, FreeSlave wrote:
> I have array of structs sorted by specific field. How can I perform binary search using this field as a key?
>
> Currently I ended up with this, but it gives error:
>
> struct S
> {
>     int i;
>     string s;
> }
>
> import std.range;
>
> void main(string [] args)
> {
>     S[] structs = [{1,"hello"}, {2,"world"}, {3, "!"}]; //sorted by i
>
>     auto sortedRange = assumeSorted!(function bool(ref const S item, int needle) {
>         return item.i < needle;
>     })(structs);
>
>     sortedRange.trisect(2); //compilation error
> }

I believe you have to pass trisect a value of S. So S(2, "") would do here, I suppose.

On Sunday, 5 April 2015 at 23:15:04 UTC, w0rp wrote:
> On Sunday, 5 April 2015 at 23:06:27 UTC, FreeSlave wrote:
>> I have array of structs sorted by specific field. How can I perform binary search using this field as a key?
>>
>> Currently I ended up with this, but it gives error:
>>
>> struct S
>> {
>>    int i;
>>    string s;
>> }
>>
>> import std.range;
>>
>> void main(string [] args)
>> {
>>    S[] structs = [{1,"hello"}, {2,"world"}, {3, "!"}]; //sorted by i
>>
>>    auto sortedRange = assumeSorted!(function bool(ref const S item, int needle) {
>>        return item.i < needle;
>>    })(structs);
>>
>>    sortedRange.trisect(2); //compilation error
>> }
>
> I believe you have to pass trisect a value of S. So S(2, "") would do here, I suppose.

Of course I could pass dummy object, but this is ugly solution. I hoped there's some better one.

I think I found solution using opBinaryRight

import std.range;

struct S
{
    int i;
    string s;

    int opCmp(int i) {
        return this.i - i;
    }

    int opCmp(ref const S s) {
        return this.i - s.i;
    }

    int opBinaryRight(string op)(int i) if (op == "<") {
        return i - this.i;
    }
}

void main(string [] args)
{
    S[] structs = [{1,"hello"}, {2,"world"}, {3, "!"}]; //sorted by i

    auto sortedRange = assumeSorted(structs);

    auto t = sortedRange.trisect(2);
}