I'm looking for neat symbols in query expressions, like "x≤3" instead of "x<=3" or "x .le. 3".

EDIT: My motivation: I have to deal with a very long list of SQL-like conditions, all squeezed into the scheme (variable, operator, value). I'd like to see this list in its most comprehensive and natural form. Replacing the verbose operators by common mathematical symbols is essential, easy to implement, and mostly trivial: = for "equals", ≤ for "le", ∍ for "contains", ... Reordering or changing the appearance of variable and value would definitively also help, but would be overkill and out of scope. My question here is just about the special symbol ≬ I've never seen before in my life.

In my attempt to simplify the clumsy expression

"x between [2, 4]" (meaning 2≤x≤4)

I've just found the promising Unicode symbol ≬, meaning between. This unknown symbol appears among the other well-known binary operators, but I don't know if it is appropriate in my context, and how to use it correctly. Is it acceptable, misleading, or even wrong to write:

"x≬[2, 4]" (meaning 2≤x≤4)

I'd be happy to use it, provided it at least resembles a valid mathematical notation.

Are there any better (more common) notations? My query language supports only lists, no intervals or sets. "x∊[2, 4]" currently means (x=2 ∨ x=4). As a compromise, I would change that into "x=[2, 4]" (ouch!) and then use "x∊[2, 4]" for 2≤x≤4. Any other ideas?

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    $\begingroup$ $x\in[2,4]$ should mean $2\le x\le 4$; $x\in\{2,4\}$ should mean $x=2$ or $x=4$ $\endgroup$ – J. W. Tanner Feb 18 '20 at 21:02
  • $\begingroup$ You seem to be asking about some particular query language, rather than common mathematical usage. If so, you'd be better at a website dealing with that language. $\endgroup$ – saulspatz Feb 18 '20 at 21:05
  • $\begingroup$ @saulspatz No, I'm just curious about the usage of ≬, because I've never seen that symbol before. The query language is just an illustration, why and how I'd like to use it—provided, it's correct. $\endgroup$ – Ralph Feb 18 '20 at 21:19
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    $\begingroup$ I have never ever seen that symbol used in mathematics and would not expect anybody to understand it without explanation. $\endgroup$ – Nate Eldredge Feb 18 '20 at 22:29
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    $\begingroup$ @saulspatz This is a Unicode symbol, and is in the group of "mathematical symbols". Whatever it means, someone in the Unicode consortium must've thought that it is useful for something. (On the other hand, as of recently Unicode has expanded so much, adding symbols such as 🤑, 👽, 👅,👩‍🍳,🎅... - that maybe the real answer is "who cares" 😉.) $\endgroup$ – Stinking Bishop Feb 18 '20 at 22:39

When you think you need a new symbol to improve the exposition of some mathematics you are free to invent or borrow one. Just explain clearly at the outset what it means.

As a general rule, be conservative. In this case Don't invent many new symbols in your document. Often words are clearer than symbols of any kind - for example, logical arguments are better in words than as statements in propositional calculus.

  • $\begingroup$ Just explain clearly at the outset what it means. — I can't, but I hoped you do. I don't want to invent some notation; I'm just willing to learn: A symbol unknown to German academics may be elementary school knowledge in America or Asia. $\endgroup$ – Ralph Feb 18 '20 at 22:42
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    $\begingroup$ @Ralph You can explaine what it means in your document. The fact that it is pretty much unknown elsewhere is an advantage - your reader is unlikely to have some other meaning in mind. $\endgroup$ – Ethan Bolker Feb 18 '20 at 23:13

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