Object equality about eo

[androidfred]

Not everything makes sense to perform equality operations on, so making everything equatable irrespective of whether there is an implementation of equality or not (like Java does) is nonsensical and dangerous.

In Haskell, only things which explicitly implement equality can have equality operations performed on them, and attempting to perform equality operations on non equatable things results in a compilation error.

[yegor256]

@g4s8 good question. I think that two objects are equal if there encapsulated attributes are equal, e.g.:

equals: // it's true
  text("hello"),
  text("hello")

[mdbs99]

...encapsulated attributes are equal,

So equals can see inside any objects?

[g4s8]

@yegor256, if I understand, equals has internal implementation to access object attributes (like java reflection)? Maybe it will be better if equals arguments implement some type? E.g.:

type Equatable:
    Bool sameAs(? other)

object equals<T as Equatable> ():
    T @first
    T @second
    ctor(T first, T second)
    Bool bool():
        first.sameAs(second)

[mdbs99]

@g4s8 I think we don't need generics, see #1.

[g4s8]

I think we don't need generics

@mdbs99, ok, but this is just an example. I mean that not any object should be equatable. For instance if, plus, minus: whether plus 4 1 is equal to plus 3 2 or not?
So if equality is not a built-in object property, then each equatable object should implement it itself. Besides object can be equal only to object with same type, and I don't know how to describe it without generics.

[NikoGJ]

equals: should be a method on the object and would require another object as an argument. You basically ask an object if he is the same as another one

[mdbs99]

@g4s8 I need to think more about that.

[Lebedevsd]

@mdbs99, @g4s8 but as far as I understand the objects plus 4 1 are not equal plus 3 2 even in java, but as types (interfaces) Number which have only one method int value() they are kind of equal.
So do we need to think about object and interface equality?
Because as an interfaces Number this two objects plus 4 1, plus 3 2 are equal.

[jachinte]

@Lebedevsd, cc. @g4s8 is there a discussion about how operators will work in EO? as far as I understand, without using syntactical sugar, plus should not be a special object, so objects plus 4 1 and plus 3 2 are objects, not values. If you want to get the result of the operation, you should ask the object to return the result; something like myPlus.value(). Then, myPlus1.value() and myPlus2.value() are equal, but plus 4 1 and plus 3 2 are not.

EDIT

There is something similar about operators and their syntax in #31

[g4s8]

@jachinte, it's not correct, plus, equals and whatever else are objects. There is no operators. The problem here is 'whether any object must be equatable and how to get object equality'.

[yegor256]

@g4s8 two objects are equal only if their datarization function results are equal

[0crat]

Job gh:cqfn/eo#60 is not assigned, can't get performer