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?

  • 3
    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
  • 2
    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
  • 1
    @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, 2023 at 18:12

4 Answers 4


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

  • 12
    So all erlang code is sad =< >= everyone else's is happy <= =>
    – Doug T.
    Nov 7, 2011 at 22:47

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 =!)


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.


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


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.