如何在Dlang中排序对象数组？

Question

如何在D中对用户定义的对象数组进行排序？

来自C++背景,我想你必须为存储在数组中的类型声明一个运算符重载,或者使用比较器函数......

如何做到这一点的一个例子将非常感激.

Answer 1

你需要std.algorithm.sort默认使用<b,所以你的类可以覆盖opCmp来利用它.

更新:只是glampert示例的替代方案.

import std.algorithm;
import std.stdio;

class Test {

    int x;

    this(int x)
    {
        this.x = x;
    }
}

void main()
{
    Test[] array = [new Test(3), new Test(1), new Test(4), new Test(2)];

    writeln("Before sorting: ");
    writeln(array.map!(x=>x.x));

    sort!((a,b)=>a.x < b.x)(array); // Sort from least to greatest

    writeln("After sorting: ");
    writeln(array.map!(x=>x.x));
}

Answer 2

使用std.algorithm.sort和opCmp过载:

import std.algorithm;
import std.stdio;

class Test 
{
    int x;

    this(int x)
    {
        this.x = x;
    }

    int opCmp(ref const Test other) const
    {
        if (this.x > other.x)
        {
            return +1;
        }
        if (this.x < other.x)
        {
            return -1;
        }
        return 0; // Equal
    }
};

void main()
{
    Test[] array = [new Test(3), new Test(1), new Test(4), new Test(2)];

    writeln("Before sorting: ");
    for (int i = 0; i < array.length; ++i)
    {
        write(array[i].x);
    }
    writeln();

    sort(array); // Sort from least to greatest using opCmp

    writeln("After sorting: ");
    for (int i = 0; i < array.length; ++i)
    {
        write(array[i].x);
    }
    writeln();
}

哪个会输出:

Before sorting:
3142
After sorting:
1234