main.go

package main

import (
	"fmt"
	"sort"
)

func formatIntPtr(fmtstr, nilstr string, p *int) string {
	if p == nil {
		return nilstr
	}

	return fmt.Sprintf(fmtstr, *p)
}

func main() {
	type P struct {
		X *int
		Y *int
	}

	Int := func(n int) *int {
		return &n
	}

	xs := []P{
		{X: Int(10), Y: Int(20)},
		{X: Int(100), Y: Int(20)},
		{X: Int(10), Y: Int(200)},
		{X: Int(100), Y: Int(200)},
		{X: nil, Y: Int(20)},
		{X: nil, Y: Int(200)},
		{X: Int(100), Y: nil},
		{X: Int(10), Y: nil},
		{X: nil, Y: nil},
	}

	cmp := func(pa, pb *int) int {
		switch {
		case pa == nil && pb == nil:
			return 0

		case pa == nil && pb != nil:
			return 1

		case pa != nil && pb == nil:
			return -1

		default:
			return *pb - *pa
		}
	}

	sort.Slice(xs, func(i, j int) bool {
		n := cmp(xs[i].X, xs[j].X)
		if n == 0 {
			n = cmp(xs[i].Y, xs[j].Y)
		}
		return n >= 0
	})

	for _, x := range xs {
		fmt.Printf(
			"(%s, %s)\n",
			formatIntPtr("%3d", "nil", x.X),
			formatIntPtr("%3d", "nil", x.Y),
		)
	}
}