# Meaning of <==> in documentation? [closed]

Title says it all. I just need to confirm that... X.__add__(y) <==> x+y ...doesn't mean anything more than just 'same as'

The problem is Google returns zero results when you search for <==>

## closed as unclear what you're asking by Gilles♦Jul 19 '16 at 10:01

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Can you at least provide a link to a page which uses this notation? – Andrej Bauer Jul 19 '16 at 6:34
• <===> is not standard notation, so it is impossible to tell. Use your common sense. – Yuval Filmus Jul 19 '16 at 6:45
• It's hard to tell without context; please give a link to where you found this. – Raphael Jul 19 '16 at 10:09
• This is probably an attempt to write "$\iff$" using ASCII symbols. It means "if and only if" in the sense of formal logics, that is "$A \iff B$" translates to "whenever $A$ is true, then $B$ is well, and vice cersa". It seems to have been misused there, though. You don't give a source, but they seems to be wanting to express either "define X.__add__(y) to mean x+y" or "X.__add__(y) is equivalent to x+y". The latter seems to match the logical operator on a superficial, English-language level, but they equivalent things are not truth values here. – Raphael Jul 19 '16 at 10:09