Compare the old way to do a multi-key sort:
https://play.golang.org/p/NJTVoeQkMt
With the new way:
https://play.golang.org/p/6ReQxHT1lR
it's a lot simpler and clearer and doesn't require a special slice type (as it did before), but lets you sort on multiple keys if you need to. Presumably sort.SliceStable is a bit slower and that's why they have a separate sort.Slice.
Note though that the old way using slice types does let you do something neater at the point of use at the cost of more setup:
OrderedBy(language, increasingLines, user).Sort(changes)
which in some ways is more similar to what you desired?Seeing this sort of hack added does make me think containers are the one big weak point in Go at present, they are a bit ugly, and special cases abound (append,delete,range,sort) - maybe in Go2 they could have something neater, more generic and more extensible. My hopes for Go 2 as a really uninformed language noob are a tidy up of the stdlib, variants and more elegant ways to manipulate containers (I won't say generics!), I would love to see things like magic comments and struct tags disappear too but that'll never happen. I'm pretty happy with the language otherwise, and would actually like to see Go get smaller and simpler over time.
Sorting is probably the one area where I really miss generics in go.. because comparing and sorting IS such a generic thing to do. In my head I think, "Oh, so I just want to do
hosts.sort(key=operator.attrgetter("os", "version", "address"))
and then proceed to write the 20 lines of code that lets me do that :-(https://play.golang.org/p/0YcxA-Ufs-
So your sorting becomes quite neat:
sort.SliceStable(changes,changes.byLines)
sort.SliceStable(changes,changes.byUser)
I think I might use it this way (haven't actually used this in a real app yet). a := ReverseOrder(10)
b := ReverseOrder(20)
a < b // false
sort.Slice(people, func(p Person) string { return ReverseOrder(p.Name) })
Comparison functions are just not very user friendly when what you really want to do is just sort naturally based on a list of fields. sort.Slice(people, func(p Person) (string, string, string, int) { return p.Country, P.Gender, p.Name, p.Age })
turns into a pretty messy comparison function.Not to mention, the key func aka DSU[1] approach is much faster when the comparison function is expensive to call.. imagine something like
sort.Slice(numbers, func(i, j int) bool { return num_factors(numbers[i]) < num_factors(numbers[j]) })
vs. sort.Slice(numbers, func(n int) int { return num_factors(n) })
One needs manual memoizing or caching of this function call, the other can do it internally in a much simpler manor.
So you can do this now:
But what I think most people want is. Since that lends to things like this: