I know eql? is used by Hashes to see if an object matches a key*, and you do
def ==(rb) if you want to support the == operator, but there must be a good reason that Hashes don’t use == instead. Why is that? When are you going to have definitions for == and eql? that are not equivalent (e.g. one is an alias to the other) ?
Similarly, why have to_ary in addition to to_a?
This question came up in response to an answer someone gave me on another question.
* Of course, a Hash also assumes eql? == true implies that the hashes codes are equal.
Also, is it basically a terribly idea to override equal? ?
I don’t know the reasoning for this particular choice in ruby, but I’ll just point out that equality is a difficult concept.
Common Lisp, for example has eq, eql, equal, equalp, and for that matter =
It can be very useful to be able to tell the difference between two references to the same object, two different objects of the same type with the same value, two objects with the same value but of different types, etc. How many variations make sense depends on what makes sense in the language.
If I recall it correctly (I don’t use ruby), rubys predicates are implementing three of these cases
== is equality of value
eql? is equality of value and type
equal? is true only for the same object