Two more examples to show off some more cool ways match could be useful.
Here, I just demonstrate how we can have logic inside matches thanks to
anonymous functions:
result = match getDayAndDate() {
"tuesday", _: "wow looks like it's tuesday",
_, 5: (func() string {
if isItWednesday() == true {
return "well, at least it's wednesday!"
} else {
return "not wednesday either!"
}
})(),
}
Here's another interesting example which showcases destructuring as well as
guards:
type date struct {
day int
month string
year int
}
func getDate() date { /* Use your imagination */ }
var today string
today = match getDate() {
date{day: d, month: m, year: y} if (m == 2) && (d > 29) :
fmt.Sprintf("Today
is impossible.", m, d, y),
date{day: d, month: m, year: y}: fmt.Sprintf("Today is %s %d, %d.", m, d
, y),
}
Nadim
Sent from my computer
On Wed, Jun 5, 2019 at 6:47 AM Nadim Kobeissi <nadim@nadim.computer> wrote:
> Hello everyone,
>
> This is my first post to this list so please excuse me if I'm not
> following all of the proper traditions for this community (posting this in
> the wrong place, etc.)
>
> I like Golang a lot and I think that it's a gift to people who love
> computer programming. I have written three softwares in Golang and I'm
> really having a great time with this language.
>
> I was wondering if people would be interested in discussing the inclusion
> of pattern matching syntax in Golang. By "pattern matching" I do not mean
> regular expressions, but rather a feature that is seen in other languages
> such as OCaml
> <https://caml.inria.fr/pub/docs/oreilly-book/html/book-ora016.html>.
>
> Rust also has this feature, which it simply calls "Patterns"
> <https://doc.rust-lang.org/1.5.0/book/patterns.html>. In particular
> Rust's implementation of this feature seems quite excellent actually.
>
> I think adding patterns/pattern matching to Golang would allow it to be
> used much more seriously in situations like building a parser, transpiler,
> compiler etc.. I'm sure there are other uses as well.
>
> Here is an example of what I have in mind:
>
> // Just some code to later demonstrate my proposition
> func getDayAndDate() (string, int) {
> date := getDate()
> if todayIsTuesday() == true {
> return "tuesday", date
> }
> return "not tuesday!", date
> }
>
> var result string
>
> // What I am proposing starts here (the below is currently not valid
> Golang code)
> result = match getDayAndDate() {
> "tuesday", _: "wow looks like it's tuesday",
> _, 5: "i don't know if it's tuesday but it's the fifth! nice!",
> "not tuesday!", _: "not a tuesday my dude",
> }
>
> Wouldn't that be cool? I don't think that existing Golang syntax allows us
> to accomplish stuff like this so elegantly. We'd have to do something
> really convoluted. The following doesn't work since switch can't handle
> functions with multiple return values:
>
> switch getDayAndDate() {
> case "tuesday", 5:
> println("cool!")
> }
>
> switch also can't handle the _ wildcard as a case value. So really there
> is no serious alternative to achieve pattern matching in Golang right now,
> as far as I can tell.
>
> I tried searching the Internet, including this mailing list, for previous
> discussions of this topic, and the only thing I could find was a post
> dating to eight years ago with little follow-up.
>
> I genuinely believe this is a great feature for Golang to pursue and I
> wonder if we can get the developers of this fantastic programming language
> and toolkit to take this feature more seriously. I'd be happy to help
> implement it myself if I can!
>
> Thank you,
>
> Nadim
> Sent from my computer
>
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