Differences of "!=" operator behavior in python3 and python2 [ bug? ]

[Steven D'Aprano]

On Mon, 13 May 2013 19:22:24 -0400, Dave Angel wrote:

> So which special methods should the <> operator call?  By rights it
> ought to call both __gt__ and __lt__ and return True if either of them
> is True.

The <> operator comes from Pascal, where it was used as "not equal" since 
ASCII doesn't include the ≠ operator. Algol 60, by contrast, used ≠ since 
it was invented before ASCII.

The use of ! as "not" is a C-ism and isn't universal.

Given the data types Pascal had as standard back when it was invented, I 
think it is fair to say that "less than, or greater than" was logically 
equivalent to "not equal to". That's no longer the case though.

Interestingly, later versions of Apple's "Standard Apple Numeric 
Environment" (SANE) included separate relational operations for "less 
than or greater than" and "not equal to". So if x was a NAN, then you 
could have pseudo-code like this:

x != y  # true

x <> y  # false



-- 
Steven