5 ms·

Am I missing something subtle? Why would you get a runtime exception if you call this function?

• jsmith45 6y ago
  The parent missed a part. If you call it with 0 you get an exception, because division by zero obviously.
  • yakubin 6y ago
    No, you don't. You get Infinity. That's how floating point works.
    • smabie 6y ago
      In most languages you get an exception
      • yakubin 6y ago
        Which languages would those be?
        • smabie 6y ago
          I guess I'm thinking of Python mostly. I thought OCaml did as well but apparently not.
        • warkdarrior 6y ago
          $ python3 Python 3.9.1 (default, Feb 3 2021, 07:04:15) [Clang 12.0.0 (clang-1200.0.32.29)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> 10 / 0 Traceback (most recent call last): File "<stdin>", line 1, in <module> ZeroDivisionError: division by zero >>>
          • yakubin 6y ago
            Although Python seems to be the exception to the rule here, your example isn't exactly right. In your example, you're performing integer division, not floating point division. In most languages, integer division by zero is indeed some kind of exception (or UB, which will most likely result in a hardware exception, causing a signal sent to the process). However, floating point division by zero is well-defined, as per definition of floating point arithmetic (in some RFCs), and most languages don't throw exceptions in this case. Python indeed seems to be the exception to the rule.
            • dthul 6y ago
              In Python 3, 1/0 is floating point division. 1//0 would be integer division.
              • yakubin 6y ago
                Right, Python2 is still the default on Debian, so I didn't notice.
• the_af 6y ago
  If you call it with argument 0 you get a runtime exception, because it results in a division by zero. It's "partial" because it's not defined for 0.
  • cies 6y ago
    So it should have been: Double -> Maybe Double That would be the "right way" to fix this. (or create a type NotNilDouble, lol)
    • bidirectional 6y ago
      Or, controversially, define 1/0 = 0.[1] [1]: https://www.hillelwayne.com/post/divide-by-zero/ https://www.hillelwayne.com/post/divide-by-zero/
      • cies 6y ago
        Enough controversy in defining std libs as it is :)
    • the_af 6y ago
      The "right" way for division by zero is controversial, though maybe that would be a solution. It's clearer for partial function "head :: [a] -> a", which takes the first of a list if it exists, and explodes without dignity if the list is empty (this is what makes head partial). A proposal is "head :: [a] -> Maybe a", so head returns Nothing when the list is empty.
      • cies 6y ago
        Idris does well here: https://www.idris-lang.org/docs/current/prelude_doc/docs/Prelude.List.html#Prelude.List.head https://www.idris-lang.org/docs/current/prelude_doc/docs/Pre...'
    • cies 6y ago
      Idris does well here: https://www.idris-lang.org/docs/current/contrib_doc/docs/Data.Nat.html#Data.Nat.divMod https://www.idris-lang.org/docs/current/contrib_doc/docs/Dat...