import std.algorithm.iteration;

import std.algorithm.sorting;

import std.stdio;

import std.typecons;

​

void main()

{

    Tuple!(string, int)[] arr = [tuple("a", 1), tuple("a", -1), tuple("b", 2), tuple("b", 25), tuple("c", 100), tuple("b", 21)];

    arr.sort!("a[0] > b[0]").chunkBy!((a, b) => a[0] == b[0]).each!writeln;

}

​