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Comment by jjgreen | Hacker News Reader

The visual difference between a ! and an l is not that great,

    send_email if !user.suspended?

    send_email if luser.suspended?

The latter could easily be an aggressive dev sending abusive emails to users they dislike enough to call lusers, at first glance at least ...

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Perhaps a Python style spelt-out `not` for boolean negation would have been a better solution for this than `unless` in deep retrospect?

    send_email if not user_suspended?

Ruby has "not", but the precedence rules between "not" and "!" differ

Well I really showed myself up as commenting on a topic that I know nothing about! :-)

But that's actually ideal in this context, a really low precedence operator is exactly what you want because you can swap `unless` for `if not` without worring about extra parentheses:

send_email if not user_suspended? || user_opt_out?

I wouldn't use this. Relying on tricky operator precedence can trip up your readers. It's better to just wrap everything in parentheses. I also use parentheses when mixing && and ||, even though their precedence relationship is (probably) more widely known.

I generally avoid `not`, `and`, `or` keywords.

Funny, when I read your point, I was sure and ready counter with an argument that code editors must highlight symbols and unary operators differently (colours, maybe spacing as well). But I just checked this on a couple of Ruby and JS highlighters and they are actually not! :scream:

Sadly `¬` never caught on. But I suppose being visually similar to `-` isn't much better.

The "logical negation" sign used to have the vertical line as long as "|", so e.g. "¬A" looked more like "‾|A" but fully vertically aligned with the letter. Sadly, this glyph fell out of usage in fonts in favour of "minus with cedilla/descender".

I'd always understood it came from Frege's Begriffsschrift, a small descender from a horizontal line (part of a larger diagram), so like a short wide T, then lost its right arm later. Would you have some examples? (a quick google images shows nothing like that ...)

It was definitely a thing in Soviet works on mathematical/symbolic logic. But here's an example from Curry [0]. As I said, it was mostly a stylistic choice.

[0] https://www.google.ru/books/edition/Foundations_of_Mathemati...

If it's not a shift+<something> key on a popular keyboard layout, it's not going to gain widespread adoption in programming.

¬ is shift+` on the most common UK keyboard layout, but yeah, it would probably need to be popular in America.

I think most of the world either uses a US layout, or other layouts that don't have that key.

Brought back memories of alt.sysadmin.recovery.

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