Update arrays-and-slices.md - added slices package tip

[swamisriman]

Added a line telling about the new "slices" package available from Go 1.21 which has slices.Equal, and that it has no issues with type

[quii]

Nice one, thanks

[swamisriman]

@quii
Sorry, it just occurred to me.
Does the slices.Equal function do a shallow check or deep check?

In the source code, they are using != to compare.
So, I assume it's a shallow compare.
https://cs.opensource.google/go/x/exp/+/master:slices/slices.go;l=24

[quii]

Yes, so it will only work with things that are comparable. With a nested slice (e.g a 2d array), it wont compile because slices are not comparable

import (
	"slices"
	"testing"
)

func TestSlicesEqual(t *testing.T) {

	t.Run("one-level slices", func(t *testing.T) {
		a := []int{1, 2, 3}
		b := []int{1, 2, 3}

		if !slices.Equal(a, b) {
			t.Fatal("strange")
		}
	})
	
	t.Run("nested", func(t *testing.T) {
		a := [][]int{
			{1, 2, 3},
			{4, 5, 6},
		}
		b := [][]int{
			{1, 2, 3},
			{4, 5, 6},
		}
		if !slices.Equal(a, b) {
			t.Fatal("strange")
		}
	})
	
}

(second test wont compile)

Could you maybe raise a 2nd PR just to clear that up for people? What do you think?

[swamisriman]

@quii
Should we add a special sub-heading for slice comparison?
As we are just introducing slices here, I didn't explain any further details as it felt like straying off the actual topic.

Or shall I just talk about the comparable part?

[swamisriman]

@quii
Raised #724