> If COPY can't be done properly, then neither can EQUAL. And, in fact, that's the case. There is no uniquely determined equality function for complex structures--there are only arbitrary ones.
What Steele says about equality is true for Scheme. Everyone has seen the famous "Wat" video of adding "{} + {}" in Ruby or JS. But no one ever mentions Scheme or Lisp:
scheme@(guile-user)> (eq? "test" "test")
$1 = #t
scheme@(guile-user)> (eqv? "test" "test")
$2 = #t
scheme@(guile-user)> (define x "test")
scheme@(guile-user)> (define y "test")
scheme@(guile-user)> (eq? x y)
$3 = #f
scheme@(guile-user)> (eqv? x y)
$4 = #f
> breaks an important mathematical property
Even mathematicians get lazy and create new syntax and short cuts to express their ideas. Programming is ultimately a human UI. It's easy to see why automatic type coercion was once popular (and probably will be again, I can almost guarantee this).
(let [x “test” y “test”]
(= x y))
; returns true with both (let) and individual (def)
Do you have some more context? I suspect somehow things are getting coerced to slices and then compared.
[0] https://github.com/rust-lang/rust/blob/e4c23daeb461ac02413eb...
Edit: it seems I don't have to wonder. Type coercion is one of the worst features IMO, and coincidentally one of his regrets:
> "One of the notorious ones was, ‘I’d like to compare a number to a string that contains that numeral. And I don’t want to have to change my code to convert the string to a number, or the number to a string. I just want it to work. Can you please make the equals operator just say, Oh this looks like a two, and this looks like a string number two. They’re equal enough.’"
> "And I did it. And that’s a big regret, because that breaks an important mathematical property, the equivalence relation property… It led to the addition of a second kind of equality operator when we standardized JavaScript.” One of the people who helped standardize JavaScript was Guy Steele, one of the co-creators of Scheme. “Guy said, ‘Don’t worry about it. There are Lisps that have five kinds of equals operators. We’ll just add another one.'"
https://thenewstack.io/brendan-eich-on-creating-javascript-i...