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Many years ago, ~2009ish, a friend pointed out that Calculator.app was giving the wrong sign when raising a positive number to a negative exponent. It turned ou

Many years ago, ~2009ish, a friend pointed out that Calculator.app was giving the wrong sign when raising a positive number to a negative exponent. It turned out to be a bug in CFNumber affecting virtually every app. I noticed the other day that you can type "1+1 sq ft in sq in=" and macOS will helpfully autocomplete the answer: 1,694.0031 square inches. Which is completely wrong. 2 square feet is 288 square inches. It took a few minutes to solve the puzzle of what the hell it is doing. So take caution trusting Apple's math, which naturally is up to 2x better³—for some value of x.

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OptionOfT 1y ago
Thank you for posting this. I had the same issue with a different calculation. The answer was wrong. I thought it looks weird because I put a space after the = and the autocomplete does not add that.
handsclean 1y ago
> 1+1 sq ft in sq in= Fun puzzle. Spoilers ahead: It seems it’s considering the first 1, and not the second, to be in square meters. “(1+1) sq ft in sq in” works.
- puce 1y ago
  1+1 sq ft = 11.76 feet^2
jb1991 1y ago
"1+1 sq ft in sq in=" The order of operations here is quite ambiguous. It’s not obvious even to a human reader how you would expect this to be interpreted.
- mulmen 1y ago
  I honestly can't tell what this would mean other than 2 square feet in inches. What's the other option?
  - fluidcruft 1y ago
    Another option could be that it's ill-posed and should just return an error.
  - fzzzy 1y ago
    (1 sq ft in sq in) + 1?
    - vrighter 1y ago
      Which sort of unit is a "sq ft in sq in" and why would they have coded it in the parser as one? It's only ambiguous if it's explicitly coded badly to induce ambiguity.
- rgovostes 1y ago
  There is a perfectly cromulent grammar for a unit-aware calculator: <expression without units> [<unit> [in <unit>]] <expression with units> [in <unit>] "1+2 feet in meters" and "1 foot + 1 meter" are both unambiguous. There is no order of operations in terms of how the units bind. The expression "1 foot + 1" is appropriately invalid. Of course the appropriate care must be paid to interpreting "in" correctly as either a unit or a keyword.

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OptionOfT 1y ago

Thank you for posting this. I had the same issue with a different calculation. The answer was wrong. I thought it looks weird because I put a space after the = and the autocomplete does not add that.

handsclean 1y ago

> 1+1 sq ft in sq in= Fun puzzle. Spoilers ahead: It seems it’s considering the first 1, and not the second, to be in square meters. “(1+1) sq ft in sq in” works.

puce 1y ago
1+1 sq ft = 11.76 feet^2

jb1991 1y ago

"1+1 sq ft in sq in=" The order of operations here is quite ambiguous. It’s not obvious even to a human reader how you would expect this to be interpreted.

mulmen 1y ago
I honestly can't tell what this would mean other than 2 square feet in inches. What's the other option?
- fluidcruft 1y ago
  Another option could be that it's ill-posed and should just return an error.
- fzzzy 1y ago
  (1 sq ft in sq in) + 1?
  - vrighter 1y ago
    Which sort of unit is a "sq ft in sq in" and why would they have coded it in the parser as one? It's only ambiguous if it's explicitly coded badly to induce ambiguity.
rgovostes 1y ago
There is a perfectly cromulent grammar for a unit-aware calculator: <expression without units> [<unit> [in <unit>]] <expression with units> [in <unit>] "1+2 feet in meters" and "1 foot + 1 meter" are both unambiguous. There is no order of operations in terms of how the units bind. The expression "1 foot + 1" is appropriately invalid. Of course the appropriate care must be paid to interpreting "in" correctly as either a unit or a keyword.