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It is very confusing that equality in JavaScript is not transitive: https://imgur.com/5pFXFbR https://imgur.com/5pFXFbR. Apparently equality in Go is no longer

by miga 6y ago

It is very confusing that equality in JavaScript is not transitive: https://imgur.com/5pFXFbR https://imgur.com/5pFXFbR. Apparently equality in Go is no longer transitive either...

jerf 6y ago
I think I'd need to see an example of that to be sure. What's talked about here doesn't really lead to that, because in these examples, values are getting passed through a function call boundary. There's a lot of rules in Go for what == does, and maybe there's something non-transitive in there, but I'd definitely need to see someone prove it on https://play.golang.org/ https://play.golang.org/ to be sure. Offhand I can't think of how to make one.
- morelisp 6y ago
  There is a nontransitive example heading this very comment section: var b *bytes.Buffer var r io.Reader = b fmt.Printf("r == nil: %v; b == nil: %v; r == b: %v\n", r == nil, b == nil, r == b) r == nil: false; b == nil: true; r == b: true
  - jerf 6y ago
    Thank you, I missed that.
  - cratermoon 6y ago
    It's not confusing if you understand that r is pointer that points to something and b is that pointer, which is nil. So of course r (the variable containing a pointer) isn't nil, b (the pointer) is nil, and r is the pointer b.
    - Dylan16807 6y ago
      Pointers don't normally compare equal to the thing they're pointing to. If it's acting as a proxy it's confusing the specific way that some things get proxied and other things don't.
      - catlifeonmars 6y ago
        Agree, r == b in this example is confusing because in all other instances, the interface{} is a kind of box type. That box type is implicitly unwrapped in the r == b comparison. Although more verbose, I’d be happy with having to do something like this for comparison: b2, ok := r.(*bytes.Buffer) equal := ok && b2 == b
      - cratermoon 6y ago
        laughs in C
nicoburns 6y ago
JavaScript is fine so long as you stick to === rather than ==. At work, == is completely banned and tjis is enforces by CI.
aikah 6y ago
> It is very confusing that equality in JavaScript is not transitive: https://imgur.com/5pFXFbR https://imgur.com/5pFXFbR. There are 2 types of equality in JS, shallow (==) and 'strict' (===). It's fine because JS is a dynamic, weakly typed language. Go isn't supposed to be.

by miga 6y ago

It is very confusing that equality in JavaScript is not transitive: https://imgur.com/5pFXFbR https://imgur.com/5pFXFbR. Apparently equality in Go is no longer transitive either...

jerf 6y ago

I think I'd need to see an example of that to be sure. What's talked about here doesn't really lead to that, because in these examples, values are getting passed through a function call boundary. There's a lot of rules in Go for what == does, and maybe there's something non-transitive in there, but I'd definitely need to see someone prove it on https://play.golang.org/ https://play.golang.org/ to be sure. Offhand I can't think of how to make one.

morelisp 6y ago
There is a nontransitive example heading this very comment section: var b *bytes.Buffer var r io.Reader = b fmt.Printf("r == nil: %v; b == nil: %v; r == b: %v\n", r == nil, b == nil, r == b) r == nil: false; b == nil: true; r == b: true
- jerf 6y ago
  Thank you, I missed that.
- cratermoon 6y ago
  It's not confusing if you understand that r is pointer that points to something and b is that pointer, which is nil. So of course r (the variable containing a pointer) isn't nil, b (the pointer) is nil, and r is the pointer b.
  - Dylan16807 6y ago
    Pointers don't normally compare equal to the thing they're pointing to. If it's acting as a proxy it's confusing the specific way that some things get proxied and other things don't.
    - catlifeonmars 6y ago
      Agree, r == b in this example is confusing because in all other instances, the interface{} is a kind of box type. That box type is implicitly unwrapped in the r == b comparison. Although more verbose, I’d be happy with having to do something like this for comparison: b2, ok := r.(*bytes.Buffer) equal := ok && b2 == b
    - cratermoon 6y ago
      laughs in C

nicoburns 6y ago

JavaScript is fine so long as you stick to === rather than ==. At work, == is completely banned and tjis is enforces by CI.

aikah 6y ago

> It is very confusing that equality in JavaScript is not transitive: https://imgur.com/5pFXFbR https://imgur.com/5pFXFbR. There are 2 types of equality in JS, shallow (==) and 'strict' (===). It's fine because JS is a dynamic, weakly typed language. Go isn't supposed to be.