4 ms·

Someone show him U+29B0 REVERSED EMPTY SET.

by pwdisswordfish9 5y ago

progbits 5y ago
Clearly useful for typesetting reflections of mathematical proofs. /s
- willis936 5y ago
  It's how Leonardo Da Vinci would type up proofs.
  - mkl 5y ago
    I think he would have typed things left to right. He only wrote in mirror because it was more ergonomic for him, but there's no such issue with a keyboard.
leipert 5y ago
Seems like Wikipedia has the answer: > When writing in languages such as Danish and Norwegian, where the empty set character may be confused with the alphabetic letter Ø (as when using the symbol in linguistics), the Unicode character U+29B0 REVERSED EMPTY SET ⦰ may be used instead
yreg 5y ago
Not long ago I found these ≤ U+2264 LESS-THAN OR EQUAL TO ⋜ U+22DC EQUAL TO OR LESS-THAN ≥ U+2265 GREATER-THAN OR EQUAL TO ⋝ U+22DD EQUAL TO OR GREATER-THAN or even ⋚ U+22DA LESS-THAN EQUAL TO OR GREATER-THAN ⋛ U+22DB GREATER-THAN EQUAL TO OR LESS-THAN
- lifthrasiir 5y ago
  The former is probably for the same reason that both plus-minus and minus-plus exist. The latter is commonly used for the "unordered" relation in partially ordered sets.
  - account42 5y ago
    Wouldn't "less than, equal to, or greater than" imply anything EXCEPT unordered?
    - lifthrasiir 5y ago
      Ah, correct. The slashed variant would mean unordered, while the original character means ordered.
- alickz 5y ago
  > ⋚ U+22DA LESS-THAN EQUAL TO OR GREATER-THAN > ⋛ U+22DB GREATER-THAN EQUAL TO OR LESS-THAN These are very interesting. What would be the use case for these?
  - a_shovel 5y ago
    Perhaps "has a comparison relation to"? So for any two numbers x and y, x ⋚ y is true, but "square ⋚ pentagon" is false.
    - skykooler 5y ago
      More concretely, it's true only for real numbers - so -4 ⋚ 7 is true, but 3+2i ⋚ 5 is false.
  - vermarish 5y ago
    When I was learning statistical hypothesis testing, I once wrote notes that looked like "H_0: mu ⋚ a <--> p-value: P(T(X) ⋛ T(a))", although I didn't include the equal-to bar.
    - mkl 5y ago
      That sounds like a different symbol: ≶ U+2276 There are lots of similar symbols: ≶≷≸≹⋚⋛⪋⪌⪏⪐⪑⪒⪓⪔
  - Nadya 5y ago
    https://en.wiktionary.org/wiki/%E2%8B%9A https://en.wiktionary.org/wiki/%E2%8B%9A > If the function f is differentiable and concave, then f′(x1)⋚f′(x2) as x1⋛x2. That is f′(x1) and f′(x2) have the opposite relation as x1 and x2.
    - bialpio 5y ago
      This blew my mind: "Related terms ⋛ (synonymous when used on its own, but antonymous when used jointly)"

Someone show him U+29B0 REVERSED EMPTY SET.

progbits 5y ago

Clearly useful for typesetting reflections of mathematical proofs. /s

willis936 5y ago
It's how Leonardo Da Vinci would type up proofs.
- mkl 5y ago
  I think he would have typed things left to right. He only wrote in mirror because it was more ergonomic for him, but there's no such issue with a keyboard.

leipert 5y ago

Seems like Wikipedia has the answer: > When writing in languages such as Danish and Norwegian, where the empty set character may be confused with the alphabetic letter Ø (as when using the symbol in linguistics), the Unicode character U+29B0 REVERSED EMPTY SET ⦰ may be used instead

yreg 5y ago

Not long ago I found these ≤ U+2264 LESS-THAN OR EQUAL TO ⋜ U+22DC EQUAL TO OR LESS-THAN ≥ U+2265 GREATER-THAN OR EQUAL TO ⋝ U+22DD EQUAL TO OR GREATER-THAN or even ⋚ U+22DA LESS-THAN EQUAL TO OR GREATER-THAN ⋛ U+22DB GREATER-THAN EQUAL TO OR LESS-THAN

lifthrasiir 5y ago
The former is probably for the same reason that both plus-minus and minus-plus exist. The latter is commonly used for the "unordered" relation in partially ordered sets.
- account42 5y ago
  Wouldn't "less than, equal to, or greater than" imply anything EXCEPT unordered?
  - lifthrasiir 5y ago
    Ah, correct. The slashed variant would mean unordered, while the original character means ordered.
alickz 5y ago
> ⋚ U+22DA LESS-THAN EQUAL TO OR GREATER-THAN > ⋛ U+22DB GREATER-THAN EQUAL TO OR LESS-THAN These are very interesting. What would be the use case for these?
- a_shovel 5y ago
  Perhaps "has a comparison relation to"? So for any two numbers x and y, x ⋚ y is true, but "square ⋚ pentagon" is false.
  - skykooler 5y ago
    More concretely, it's true only for real numbers - so -4 ⋚ 7 is true, but 3+2i ⋚ 5 is false.
- vermarish 5y ago
  When I was learning statistical hypothesis testing, I once wrote notes that looked like "H_0: mu ⋚ a <--> p-value: P(T(X) ⋛ T(a))", although I didn't include the equal-to bar.
  - mkl 5y ago
    That sounds like a different symbol: ≶ U+2276 There are lots of similar symbols: ≶≷≸≹⋚⋛⪋⪌⪏⪐⪑⪒⪓⪔
- Nadya 5y ago
  https://en.wiktionary.org/wiki/%E2%8B%9A https://en.wiktionary.org/wiki/%E2%8B%9A > If the function f is differentiable and concave, then f′(x1)⋚f′(x2) as x1⋛x2. That is f′(x1) and f′(x2) have the opposite relation as x1 and x2.
  - bialpio 5y ago
    This blew my mind: "Related terms ⋛ (synonymous when used on its own, but antonymous when used jointly)"