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Wikipedia says:

Not equal

The symbol used to denote inequation — when items are not equal — is a slashed equals sign "≠" (Unicode 2260).

Most programming languages, limiting themselves to the ASCII character set, use ~=, !=, /=, =/=, or <> to represent their boolean inequality operator.

All of these operators can be found in this table, apart from =/=. I can find this equals-slash-equals used as a way of formatting ≠ in plaintext but not in any programming language.

Has =/= been used as the inequality operator in any programming language?

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    It might help if you explain why you care, what problem you're trying to solve. "any programming language" is a pretty wide field; it seems likely that there was some language somewhere in the history of computing that used =/=, but not so likely that a well-known language does. It'd be simple enough to create a language that accepts =/= for not equal, but I don't expect that'd help. So... why do you care, and how is this question constructive?
    – Caleb
    Nov 7, 2011 at 10:51
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    It's not used because not only does it require 3 characters instead of 2 (!=) it's also a really ugly way to represent the slashed equals sign.
    – Ben Brocka
    Nov 7, 2011 at 13:27
  • Thanks for asking this... I was searching for /= in Haskell and just reading the meta description for this page told me what it was.
    – Aditya M P
    Aug 6, 2013 at 4:07
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    @BenBrocka "ugly" is of course subjective. In the long list of attempts to approximate ≠ in ASCII, I'd argue =/= may be the clearest on first viewing - and among the most annoying to type forever after. :) I vaguely recall some language that used #, which is also not in the Wikipedia table, so I wouldn't assume the latter to be exhaustive.
    – Mark Reed
    Mar 9, 2016 at 12:49
  • Ah, it was Modula-2; it recognizes <>, like the rest of the Pascal family, but also accepts #.
    – Mark Reed
    May 19 at 18:12

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Yes, it is in Erlang. =/= means exactly not equal to, that would be somewhat equivalent to !==.

See more subtle differences (such as =< instead of <=) here: http://www.erlang.org/doc/reference_manual/expressions.html#id198443

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    So all erlang code is sad =< >= everyone else's is happy <= =>
    – Doug T.
    Nov 7, 2011 at 22:47
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In the long list of languages that don't use =/=, PROLOG uses X =\= Y as "the values X and Y are not equal", as opposed to the equality operator =:=. (Equality, not to be confused with the unification operator =!)

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In Swift, you can define an operator with this name, same priority and associativity as !=, and add implementations corresponding to each implementation of != by calling the != operator.

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Erlang does. The following lists all operators: https://www.tutorialspoint.com/erlang/erlang_operators.htm

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