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    While the 3-character "spaceship operator" sequence "<=>" looks similar to "⇔", it's heavily overridden in computing contexts. It means "three way comparison" in several programming languages, or "null-safe equality check" in SQL dialects. Math markup in prose is generally an anti-pattern, as symbol sequences are typically opaque to the non-cognoscenti: so "iff" is trivially searchable, but "⇔" is not. Overall, I'd consider "iff" far more likely to be unambiguous and colloquially known to those reading an English computer manual, but I'd recommend "if and only if" for most cases. Commented Nov 20, 2024 at 3:02
  • A reader could think I meant to suggest the single-character double-arrow symbol. I can fix that. Thanks. Commented Nov 20, 2024 at 16:03
  • But the spaceship operator doesn't ever mean iff in computing contexts, so far as I can tell. It means "3-way comparison", or "null-safe comparison"; a comparator, not a conditional operator. Your line "It's a real logic symbol, which officially means the same thing as IFF" does not appear to be correct, or at least, your link does not seem to support the claim you're making that it's ever used or understood to mean "IFF" by anyone other than yourself. Commented Nov 21, 2024 at 3:30
  • @DewiMorgan Ah! You think I'm one of those naive folks who "helpfully" propose a solution they just made up! You think I hastily misread a Wikipedia article. No. I learned <=> in the same computer logic class I learned IFF, and have seen it since used interchangeably. I assure you that if you make truth tables, IFF and <=> work out to be identical. Commented Nov 21, 2024 at 18:33
  • I can see this working out very badly in things like Javadoc comments, which are (approximately) HTML. Commented Nov 21, 2024 at 22:09