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II2II • yesterday at 2:12 PM • 2 replies • view on HN

> Calculators are deterministically correct

Calculators are deterministic, but they are not necessarily correct. Consider 32-bit integer arithmetic:

  30000000 * 1000 / 1000
  30000000 / 1000 * 1000
Mathematically, they are identical. Computationally, the results are deterministic. On the other hand, the computer will produce different results. There are many other cases where the expected result is different from what a computer calculates.

Replies

wongarsu • yesterday at 2:18 PM

A good calculator will however do this correctly (as in: the way anyone would expect). Small cheap calculators revert to confusing syntax, but if you pay $30 for a decent handheld calculator or use something decent like wolframalpha on your phone/laptop/desktop you won't run into precision issues for reasonable numbers.

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anthk • yesterday at 2:27 PM

Good languages with proper number towers will deal with both cases in equal terms.