23

Googling this question has proved somewhat useless, so the ¬ symbol:

  • What is it for?
  • What is is called?
  • Is it used in any programming languages?
  • 1
    That character is U+00AC NOT SIGN and is one of the many notations for logical negation – amon Jul 19 '15 at 18:49
  • 5
    I'm voting to close this question as off-topic because it is not about software development concepts as explained in the help center. – amon Jul 19 '15 at 18:50
  • 1
    It's on a standard UK 101 keyboard, top left with the back tick ` ` ` and the broken pipe ¦. – BanksySan Jul 19 '15 at 19:26
  • 2
    Wikipedia has redirects for many unicode symbols. ¬. You can also see this with things like 🍩. While google's search doesn't do a good job with this character, one should try pasting it into Wikipedia's search. They have many redirects for single unicode characters set up. – user40980 Jul 20 '15 at 2:23
  • 1
    Used to break long statements in app script alvinalexander.com/mac-os-x/… – Maxim Veksler May 15 '16 at 9:53
31

The only use I've seen for the ¬ symbol is to represent negation in the context of formal logic. For instance, if P is the proposition "It will rain today", then ¬P is the proposition "It will not rain today." I've also seen ~ used for this.

I don't believe it has an actual name other than "negation symbol". Normally it's read as "not".

As far as I know, in programming this symbol has no special meaning, at least not in any mainstream languages I've used.

  • Some programming languages accept UTF8 characters as names or user-defined operators. – Basile Starynkevitch Jul 19 '15 at 19:17
  • 1
    Why is negation symbol not an "actual name"? After all, we call ! exclamation point and ? question mark. And those are perfectly fine names. – Brandin Jan 26 '16 at 19:42
  • REXX uses ¬ for logical not and in operators like ¬=, ¬>, etc. Most implementation also allow `\` because many keyboards lack a ¬ key. I'm not sure that it can be considered a mainstream language, though. – mrb Aug 8 '16 at 13:33
  • PL/1 (developed in the late 1960s) used the ¬ symbol for not. Having used PL/1 for many years I still think of this as the not symbol – Kickstart Jul 6 '17 at 10:53
  • AppleScript uses ¬ as the line-continuation symbol, to split long commands into multiple lines, like \ in bash script. – Chad von Nau Jun 30 '18 at 22:39

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