import std.stdio;

import std.container;

import std.range;

import std.algorithm;

​

struct S

{

    string id;

    int amount;

}

​

bool same(S s1, S s2)

{

    return s1.id == s2.id;

}

​

void addUp(ref S s1, ref S s2)

{

    s1.amount += s2.amount;

}

​

void conflate(ref DList!S list)

{

    auto iterate = list[];

    while (!iterate.empty)

    {

        auto p = iterate.front;

        iterate.popFront();

        list[].filter!(a => same(a, p))

            .each!(a => addUp(p, a));

        list.stableRemove(list[].filter!(a => !same(a, p)));

    }

}

​

void main()

{

    DList!S list = [

        S("a", 1), S("b", 2), S("a", 2), S("c", 5), S("b", 2), S("a", 3)

    ];

​

    conflate(list);

    writeln(list[]); //expected output [A("a", 6), A("b",4), A("c",5)]

}