a == b == c is a very nice construct. a < b > c too. however julia allows a != b != c, but i would call it contraintuitive, because it is true if a == c. my thinking is that != should not allow this at all, for it lacks common sense meaning. but if it is allowed, i would suggest translate to a != b &…

I hadn’t even realized that a == b == c was lowered that way, instead of how it would be in C/C++ and C-like languages. I would have thought that it would mean something totally different, i.e. (a == b) == c, which then return true if c were either Bool or something that converted to true or false …

[image] ScottPJones: I hadn’t even realized that a == b == c was lowered that way, instead of how it would be in C/C++ and C-like languages. See http://docs.julialang.org/en/stable/manual/mathematical-operations/#chaining-comparisons

Ah, thanks! I also wasn’t trying to imply that it wasn’t well documented somewhere, just that it might be worth having a line in at least the C/C++ differences section (which I was the initial author of ages ago). What do you think of doing that? (and pointing a reference to the chaining compariso…

I must say that I find the current meaning of a != b != c to be exactly what I intuitively expected, and I was thoroughly confused as to what you even meant at first. I read it like this: a is different from b and b is different from c. So julia> 1 != 2 != 1 true is exactly as it should be. If yo…

[image] DNF: I must say that I find the current meaning of a != b != c to be exactly what I intuitively expected, and I was thoroughly confused as to what you even meant at first. I think you’re getting at the real problem with this kind of discussion: people don’t all have the same intuition…

[image] Evizero: Even a < b < c does not assume transitivity It should be in all cases (as logic dictates), the expand you showed, only shows what the current implementations of Julia does. In case when you do not have transitive, e.g. a < b > c, or != or the sneaky ≈ (isapprox), then for th…

[image] pint: is there a use case in which < is not transitive? I believe no… but math has a way of surprising me… I don’t know half of it… E.g. I didn’t give this much though until I realized (with more advanced “numbers” they lose more properties): For complex number (and matrices of anyth…

[image] Palli: It should be in all cases (as logic dictates), the expand you showed, only shows what the current implementations of Julia does. You’re now actively spreading misinformation. Please stop.

[image] pint: is there a use case in which < is not transitive? A linked list chain where you define a<b to mean a is immediately to the left of b? That sounds like a perfectly useful and valid dispatch for < for which it wouldn’t be transitive. As @stevengj noted, it’s just an operator, so y…

[image] ChrisRackauckas: A linked list chain where you define a<b to mean a is immediately to the left of b? That sounds like a perfectly useful and valid dispatch for < for which it wouldn’t be transitive. not to me. < has a very specific meaning, and it means “comes before” in some ordering…

A != b != c

Internals & Design

johnmyleswhite January 9, 2017, 8:58pm 19

You’re now actively spreading misinformation. Please stop.

Speculation chained comparison optimization (possibly with outlining)

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A != b != c

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