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Which one below is correct?

NOTE There are explanations inside the answers. Even if you know the answer please try to select all of them one by one, so you can read the explanations.

1. You can run a library package.
2. In a library package, there should be a function named main (func main).
3. You can compile a library package. CORRECT
4. You have to compile a library package.

1: You can't, but you can import it from other packages.

2: In a library package, you don't have to include the main function. Because it isn't an executable package. Only in executable packages you need a main func.

4: You don't have to compile it. When you import it, it will automatically be built by the other program or library when it gets compiled or ran.

What do you need to export a name?

1. You need to type it in all capital letters
2. You need to type its first letter as a capital letter CORRECT
3. You need to put it inside a function scope
4. You need to create a new file for that name

1: When you do so, it will be exported, that's true, but don't do that; so I assume that this answer is not correct :)

2: That's right. Then the other packages can access it.

3: It should be in a package scope, not function scope.

4: You don't have to do that.

How can you use a function from your library from an executable program?

1. You need to export your library package first; then you can access its imported names
2. You need to import your library package first; then you can access its exported names CORRECT
3. You can access your library package as if it's in your executable program
4. You can import it just by using its name

1: You can't export packages. All packages are already exported. Unless you put them in a directory called: "internal". But, that's an advanced topic for now.

2: That's right.

3: You can't access a package from another package without importing it.

4: No, you can't. You need to import it using its full directory path after GOPATH. BTW, in the near future, this may change with the Go modules support.

In the following program, which names are exported?

package wizard

import "fmt"

func doMagic() {
    fmt.Println("enchanted!")
}

func Fireball() {
    fmt.Println("fireball!!!")
}

1. fmt
2. doMagic
3. Fireball CORRECT
4. Println

1: That's just an imported package name.

2: It starts with a lowercase letter; so, it's not exported.

3: That's right. It starts with a capital letter.

4: This isn't your function. It's already been exported in the fmt package. But, it isn't exported here.

In the following program, which names are exported?

package wizard
import "fmt"

var one string
var Two string
var greenTrees string

func doMagic() {
    fmt.Println("enchanted!")
}

func Fireball() {
    fmt.Println("fireball!!!")
}

1. doMagic and Fireball
2. Fireball and Two CORRECT
3. Fireball, greenTrees and Two
4. Fireball, greenTrees, one and Two

1: doMagic starts with a lowercase letter; so, it's not exported.

2: That's right. Fireball and Two, they both start with a capital letter.

3: greenTrees starts with a lowercase letter; so, it's not exported.

4: one and greenTrees do not start with capital letters; so, they're not exported.