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I am watching the keynote, it looks interesting. I don't know Go at all, though I know several languages including C. I don't quite know what he is talking abo

by canadev 12y ago

I am watching the keynote, it looks interesting. I don't know Go at all, though I know several languages including C. I don't quite know what he is talking about when he talks about main and initialization. Can anyone elaborate on this for me? I hate to say this because I feel like a jerk in doing so, but I'm about 25 minutes in and the little gopher that scrolls across the screen (some sort of advertisement, I think) is so distracting. It is awful.

leaveyou 12y ago
Function main() in package "main" is the entry point for a Go application but it is not the first code that gets executed when you start a Go app. Each package can have an init() function which gets executed in the order of dependency (if pkg A imports pkg B then B.init() is executed before A.init()) before main.main() is executed.
- canadev 12y ago
  I see. Thank you.
- Laremere 12y ago
  It's slightly more complicated than that: In addition to the init() function, variables on the package level can be initialized during initialization too. For example: http://play.golang.org/p/tvlX7cqaaB http://play.golang.org/p/tvlX7cqaaB This is important for package level variables such as arrays. Since there are only a very limited number of types which can be constants in Go, everything else which you'd use like a constant needs to be initialized.
  - leaveyou 12y ago
    If we go in details, we can also add that goroutines created in init() or at init time are effectively started only after all init() functions finish.
chubot 12y ago
Not a Go expert, but I think it has to do with global variables/constants in modules. In C, what can run before main() is extremely limited. In C++, much more can happen before main(), i.e. running constructors for static objects, and the initialization order is undefined (this is a pretty well known problem). I guess in Go you can also have relatively elaborate static initialization, so it has a similar problem as C++? Interested if any Go users can elaborate on this.
- pjmlp 12y ago
  Like in the Object Pascal/Modula-2 language family, you can define a package initialization sections. There are executed before control reaches main, and you need to have import relationships into consideration.
bketelsen 12y ago
The gophers are being removed by popular demand.
- canadev 12y ago
  Nice!

by canadev 12y ago

leaveyou 12y ago

Function main() in package "main" is the entry point for a Go application but it is not the first code that gets executed when you start a Go app. Each package can have an init() function which gets executed in the order of dependency (if pkg A imports pkg B then B.init() is executed before A.init()) before main.main() is executed.

canadev 12y ago
I see. Thank you.
Laremere 12y ago
It's slightly more complicated than that: In addition to the init() function, variables on the package level can be initialized during initialization too. For example: http://play.golang.org/p/tvlX7cqaaB http://play.golang.org/p/tvlX7cqaaB This is important for package level variables such as arrays. Since there are only a very limited number of types which can be constants in Go, everything else which you'd use like a constant needs to be initialized.
- leaveyou 12y ago
  If we go in details, we can also add that goroutines created in init() or at init time are effectively started only after all init() functions finish.

chubot 12y ago

Not a Go expert, but I think it has to do with global variables/constants in modules. In C, what can run before main() is extremely limited. In C++, much more can happen before main(), i.e. running constructors for static objects, and the initialization order is undefined (this is a pretty well known problem). I guess in Go you can also have relatively elaborate static initialization, so it has a similar problem as C++? Interested if any Go users can elaborate on this.

pjmlp 12y ago
Like in the Object Pascal/Modula-2 language family, you can define a package initialization sections. There are executed before control reaches main, and you need to have import relationships into consideration.

bketelsen 12y ago

The gophers are being removed by popular demand.

canadev 12y ago
Nice!