why do we need primary constructors about eo

[yegor256]

@g4s8 but the order of parameters we can infer from the order of object attributes. In this example:

object alphabet as Book:
  Text @isbn
  Text @title
  ctor()
    alphabet:
      "978-1-51916-691-3",
      "The Alphabet"
  ctor(String i, String t):
    @isbn = i
    @title = t

We know that @isbn goes first and @title goes next. What is the point of repeating this fact again in a constructor?

[aravindps]

@yegor256 It is okay, if the main constructor is used only for setting values to all the attributes. What happens for derived attributes or constants in the object?

Player player = Player.new("a"){
	String .name
	int .overallScore
	new(String name) {
	    .name = name
	    .overallScore = 0
	}
}

If the constructor allows has named arguments, it makes sense.

Player player = Player.new(name="a"){
	String .name
	int .overallScore
	new(String name) {
	    .name = name
	    .overallScore = 0
	}
}

[mdbs99]

@yegor256 always will exists a primary constructor, even if you don't create one.
I mean, all constructor we create will be a second.
So I think we can forget this ticket.

[NikoGJ]

In some old programming languages, programs were made of 2 distincts parts, the declaration part with the initialization of variables and the actual code which is using them.

I wonder if this "usage" could be applied to OO....
Can we imagine an object having 2 modes, an initialization mode which would be just basic linking object attributes and setup, and a runtime mode (the actual simulation mode made of method calls between objects, the one that we're used to). 2 opaque and isolated worlds.

It's just an idea though, I'm saying this because what we do when creating objects and initialize their state require a different set of methods than when we use them..

[yegor256]

@aravindps in this case we just create a primary ctor, which accepts all arguments and then a secondary one, which provides defaults:

Player player = Player.new("a"){
	String .name
	int .overallScore
	new(String name) {
	    new(name, 0)
	}
	new(String name, int score) {
	    .name = name
	    .overallScore = score
	}
}

[g4s8]

I think that we need primary constructor declaration (without any code or attribute initialization) to specify parameters order. Without it attributes initialization may be ambiguous. E.g. object from Readme:

object alphabet as Book:
  Text @isbn
  Text @title
  ctor()
    alphabet:
      "978-1-51916-691-3",
      "The Alphabet"
  ctor(String i, String t):
    @isbn = i
    @title = t
  Text asText():
    sprintf:
      "ISBN is %s, title is '%s'",
      @isbn,
      @title

It's not clear (without primary constructor) where is title and where is isbn, because both paraeters are strings:

ctor()
    alphabet:
      "978-1-51916-691-3",
      "The Alphabet"

So I suggest to declare primary constructor like this:

ctor(String isbn, String title)

• without body
• without colon
• parameter names are same as attribute names

@yegor256 , what do you say?

[g4s8]

We know that @isbn goes first and @title goes next. What is the point of repeating this fact again in a constructor?

Looks logical, in this way we don't need primary constructors at all.

[yegor256]

@g4s8 I think it's important to update README too, after #112

[g4s8]

@yegor256 done!

[yegor256]

@g4s8 thanks a lot!