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  4. Ever heard of casting?

Ever heard of casting?

Scheduled Pinned Locked Moved The Weird and The Wonderful
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  • L Luc Pattyn

    chevu wrote:

    This one is correct code

    wrong again: 1. the result for pow=18 is wrong. 2. pow=5 and pow=6 give the same result??? I think you have abundantly proven now that your code has high debugging complexity. :(

    Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


    I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


    C Offline
    C Offline
    chevu
    wrote on last edited by
    #19

    sorry dude... i had really forget to check till 18... coz of odd even cases that code will fail... I knw you people are getting irritated by now, but you can check this code

    double pow(long long a, long long b)
    {
    if(b == 0)
    return 1.0;
    else if(b == 1)
    return a;
    else if(b%2 == 0)
    return pow(a*a,b/2);
    else
    return a* pow(a*a,b/2);
    }

    i have tested this code upto long long limits...

    S J 2 Replies Last reply
    0
    • C chevu

      sorry dude... i had really forget to check till 18... coz of odd even cases that code will fail... I knw you people are getting irritated by now, but you can check this code

      double pow(long long a, long long b)
      {
      if(b == 0)
      return 1.0;
      else if(b == 1)
      return a;
      else if(b%2 == 0)
      return pow(a*a,b/2);
      else
      return a* pow(a*a,b/2);
      }

      i have tested this code upto long long limits...

      S Offline
      S Offline
      Stanciu Vlad
      wrote on last edited by
      #20

      Recursive functions brings color in life :-D

      I have no smart signature yet...

      1 Reply Last reply
      0
      • C chevu

        sorry dude... i had really forget to check till 18... coz of odd even cases that code will fail... I knw you people are getting irritated by now, but you can check this code

        double pow(long long a, long long b)
        {
        if(b == 0)
        return 1.0;
        else if(b == 1)
        return a;
        else if(b%2 == 0)
        return pow(a*a,b/2);
        else
        return a* pow(a*a,b/2);
        }

        i have tested this code upto long long limits...

        J Offline
        J Offline
        J4amieC
        wrote on last edited by
        #21

        chevu wrote:

        long long a

        If I were a canadian, thats how I would describe this thread.

        modified on Thursday, March 4, 2010 8:11 AM

        C 1 Reply Last reply
        0
        • J J4amieC

          chevu wrote:

          long long a

          If I were a canadian, thats how I would describe this thread.

          modified on Thursday, March 4, 2010 8:11 AM

          C Offline
          C Offline
          chevu
          wrote on last edited by
          #22

          what kind of comment was that?

          J 1 Reply Last reply
          0
          • C chevu

            what kind of comment was that?

            J Offline
            J Offline
            J4amieC
            wrote on last edited by
            #23

            Erm, a half-assed joke, you douche.

            1 Reply Last reply
            0
            • L Luc Pattyn

              chevu wrote:

              how can you say algo i gave takes more time to debug.. complexity of given algo is O(n)

              O(n) and O(lg(n)) apply to execution time, not debugging time. There are no formulas for debugging time; it depends on number of statements, decision points, readability of code, and initial number of bugs. Your code has more than 5 bugs, it will take you lots of time to find all of them. I suggest you try and fix and run it until the result is correct. :|

              Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


              I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


              J Offline
              J Offline
              johannesnestler
              wrote on last edited by
              #24

              thank you for answering to chevu - he didn't get the hint - "debug time" :rose:

              1 Reply Last reply
              0
              • C chevu

                sorry i messed up with code... This one is correct code

                decimal res = 10;
                decimal multi = 10;
                decimal rem = 1;
                int pow = 18;//For pow 0 you can directly return with 0

                while(pow > 1)
                {
                res *= res;
                rem *= (pow%2)? multi:1;
                pow /= 2;
                }
                res *= rem;

                L Offline
                L Offline
                Lost User
                wrote on last edited by
                #25

                Here's how:

                    static decimal pow(decimal x, **u**int n)
                    {
                        decimal result = 1;
                        while (n > 0)
                        {
                            if ((n & 1) == 1)
                            {
                                result \*= x;
                            }
                            n >>= 1;
                            if (n == 0)
                                break;   //not nice, but needed in case x\*x overflow on the last step
                            x \*= x;
                        }
                        return result;
                    }
                

                Good luck! ok so it's not the best possible code, I just hacked it together, but it works (tested)

                modified on Friday, March 5, 2010 11:40 AM

                L 1 Reply Last reply
                0
                • L Lost User

                  Here's how:

                      static decimal pow(decimal x, **u**int n)
                      {
                          decimal result = 1;
                          while (n > 0)
                          {
                              if ((n & 1) == 1)
                              {
                                  result \*= x;
                              }
                              n >>= 1;
                              if (n == 0)
                                  break;   //not nice, but needed in case x\*x overflow on the last step
                              x \*= x;
                          }
                          return result;
                      }
                  

                  Good luck! ok so it's not the best possible code, I just hacked it together, but it works (tested)

                  modified on Friday, March 5, 2010 11:40 AM

                  L Offline
                  L Offline
                  Luc Pattyn
                  wrote on last edited by
                  #26

                  harold aptroot wrote:

                  (tested)

                  that is unacceptable. This is the Coding Horrors forum after all. You're expected to publish something that is completely wrong, yet claim it is correct. :)

                  Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


                  I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


                  L 1 Reply Last reply
                  0
                  • L Luc Pattyn

                    harold aptroot wrote:

                    (tested)

                    that is unacceptable. This is the Coding Horrors forum after all. You're expected to publish something that is completely wrong, yet claim it is correct. :)

                    Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


                    I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


                    L Offline
                    L Offline
                    Lost User
                    wrote on last edited by
                    #27

                    Oops! Sorry :)

                    L 1 Reply Last reply
                    0
                    • L Lost User

                      Oops! Sorry :)

                      L Offline
                      L Offline
                      Luc Pattyn
                      wrote on last edited by
                      #28

                      No problem. Anyway, it fails for negative n. :)

                      Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


                      I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


                      L 1 Reply Last reply
                      0
                      • L Luc Pattyn

                        No problem. Anyway, it fails for negative n. :)

                        Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


                        I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


                        L Offline
                        L Offline
                        Lost User
                        wrote on last edited by
                        #29

                        It's not supposed to work for negative n anyway

                        L 1 Reply Last reply
                        0
                        • L Lost User

                          It's not supposed to work for negative n anyway

                          L Offline
                          L Offline
                          Luc Pattyn
                          wrote on last edited by
                          #30

                          I didn't see any specs; you could have tested and thrown an InvalidArgumentException; or made the second parameter a uint. [EDIT]Negative exponents result in divisions, which for integers tend to yield either 0 or 1 depending on the value of a.[/EDIT] :)

                          Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


                          I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


                          L 1 Reply Last reply
                          0
                          • L Luc Pattyn

                            I didn't see any specs; you could have tested and thrown an InvalidArgumentException; or made the second parameter a uint. [EDIT]Negative exponents result in divisions, which for integers tend to yield either 0 or 1 depending on the value of a.[/EDIT] :)

                            Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]


                            I only read code that is properly formatted, adding PRE tags is the easiest way to obtain that.


                            L Offline
                            L Offline
                            Lost User
                            wrote on last edited by
                            #31

                            Is that really necessary..? Fortunately adding just 1 letter of code takes the problem away.

                            1 Reply Last reply
                            0
                            • A ArchimaX

                              This is an excerpt from some sample code provided in the documentation for an EFT interface

                              decimal divider;
                              // we need 10^18, but Math.Pow does not support decimal
                              // types and decimal does not provide a power function
                              divider = 10*10*10;
                              divider = Decimal.Multiply(divider,10*10*10*10*10);
                              divider = Decimal.Multiply(divider,10*10*10*10*10);
                              divider = Decimal.Multiply(divider,10*10*10*10*10);

                              Blows my mind :-)

                              R Offline
                              R Offline
                              Rob Grainger
                              wrote on last edited by
                              #32

                              Not sure a cast is the best approach here - decimal types are OK for currency and other situations where accuracy is critical. Floating point types can introduce rounding errors - it all depends how the value is used. Best solution I've seen in the comments is 1E18M, but really 1E19M may be better ;-)

                              A 1 Reply Last reply
                              0
                              • R Rob Grainger

                                Not sure a cast is the best approach here - decimal types are OK for currency and other situations where accuracy is critical. Floating point types can introduce rounding errors - it all depends how the value is used. Best solution I've seen in the comments is 1E18M, but really 1E19M may be better ;-)

                                A Offline
                                A Offline
                                Avi Berger
                                wrote on last edited by
                                #33

                                Yes! I'm sorry I could only give you one five. When the problem domain calls for decimal calculations rather than floating point, casting from a floating point type would be a greater horror.

                                Please do not read this signature.

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