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  4. It's Primes as far as the eye can see!

It's Primes as far as the eye can see!

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  • OriginalGriffO Offline
    OriginalGriffO Offline
    OriginalGriff
    wrote on last edited by
    #1

    This is the whole of a would-be Tip submitted today:

    public class Class1
    {
    static void Main(string[] args)
    {
    Console.WriteLine("Enter a Number");
    int num = int.Parse(Console.ReadLine());
    for (int i = 1; i <=num ; i++)
    {
    if(i==2)
    Console.WriteLine(2);

                if (i % 2 != 0)
                {
                    Console.WriteLine(i);
                }
            }
    
         }
    }
    

    No text, no explanation - the author (I can only assume he works for Mindfire, it's about their level) clearly felt that it spoke for itself. And boy, does it ever! This, ladies-n-gentlemen, is a Prime Number generator according to the author. So...I tried it... According to this code, the prime numbers under 26 are:

    1
    2
    3
    5
    7
    9
    11
    13
    15
    17
    19
    21
    23
    25

    Now, call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3, and both 15 and 25 were divisible by 5... So which is wrong? The Code? Or the Laws of Mathematics? Only the author can tell... :laugh:

    Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

    "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
    "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

    Z I N P P 9 Replies Last reply
    0
    • OriginalGriffO OriginalGriff

      This is the whole of a would-be Tip submitted today:

      public class Class1
      {
      static void Main(string[] args)
      {
      Console.WriteLine("Enter a Number");
      int num = int.Parse(Console.ReadLine());
      for (int i = 1; i <=num ; i++)
      {
      if(i==2)
      Console.WriteLine(2);

                  if (i % 2 != 0)
                  {
                      Console.WriteLine(i);
                  }
              }
      
           }
      }
      

      No text, no explanation - the author (I can only assume he works for Mindfire, it's about their level) clearly felt that it spoke for itself. And boy, does it ever! This, ladies-n-gentlemen, is a Prime Number generator according to the author. So...I tried it... According to this code, the prime numbers under 26 are:

      1
      2
      3
      5
      7
      9
      11
      13
      15
      17
      19
      21
      23
      25

      Now, call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3, and both 15 and 25 were divisible by 5... So which is wrong? The Code? Or the Laws of Mathematics? Only the author can tell... :laugh:

      Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

      Z Offline
      Z Offline
      ZurdoDev
      wrote on last edited by
      #2

      OriginalGriff wrote:

      call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3

      Ya, but that's also back when Pluto was a planet. We live in a very different place now. This user submitted this in QA, got closed, and resubmitted it in QA. I told him to post as a tip but apparently he didn't realize some explanation should be added. Or, the important part, THAT IT SHOULD WORK! :laugh:

      There are only 10 types of people in the world, those who understand binary and those who don't.

      OriginalGriffO D 2 Replies Last reply
      0
      • OriginalGriffO OriginalGriff

        This is the whole of a would-be Tip submitted today:

        public class Class1
        {
        static void Main(string[] args)
        {
        Console.WriteLine("Enter a Number");
        int num = int.Parse(Console.ReadLine());
        for (int i = 1; i <=num ; i++)
        {
        if(i==2)
        Console.WriteLine(2);

                    if (i % 2 != 0)
                    {
                        Console.WriteLine(i);
                    }
                }
        
             }
        }
        

        No text, no explanation - the author (I can only assume he works for Mindfire, it's about their level) clearly felt that it spoke for itself. And boy, does it ever! This, ladies-n-gentlemen, is a Prime Number generator according to the author. So...I tried it... According to this code, the prime numbers under 26 are:

        1
        2
        3
        5
        7
        9
        11
        13
        15
        17
        19
        21
        23
        25

        Now, call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3, and both 15 and 25 were divisible by 5... So which is wrong? The Code? Or the Laws of Mathematics? Only the author can tell... :laugh:

        Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

        I Offline
        I Offline
        Ian Shlasko
        wrote on last edited by
        #3

        You know, as someone who's been messing around in Project Euler lately and could now code a Sieve of Eratosthenes* in his sleep, that algorithm makes me cry a little inside. (You know, it's easier to code the algorithm than to spell that guy's name...)

        Proud to have finally moved to the A-Ark. Which one are you in?
        Author of the Guardians Saga (Sci-Fi/Fantasy novels)

        1 Reply Last reply
        0
        • Z ZurdoDev

          OriginalGriff wrote:

          call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3

          Ya, but that's also back when Pluto was a planet. We live in a very different place now. This user submitted this in QA, got closed, and resubmitted it in QA. I told him to post as a tip but apparently he didn't realize some explanation should be added. Or, the important part, THAT IT SHOULD WORK! :laugh:

          There are only 10 types of people in the world, those who understand binary and those who don't.

          OriginalGriffO Offline
          OriginalGriffO Offline
          OriginalGriff
          wrote on last edited by
          #4

          RyanDev wrote:

          back when Pluto was a planet.

          What? You mean he wasn't always a dog? :omg:

          Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

          "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
          "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

          1 Reply Last reply
          0
          • OriginalGriffO OriginalGriff

            This is the whole of a would-be Tip submitted today:

            public class Class1
            {
            static void Main(string[] args)
            {
            Console.WriteLine("Enter a Number");
            int num = int.Parse(Console.ReadLine());
            for (int i = 1; i <=num ; i++)
            {
            if(i==2)
            Console.WriteLine(2);

                        if (i % 2 != 0)
                        {
                            Console.WriteLine(i);
                        }
                    }
            
                 }
            }
            

            No text, no explanation - the author (I can only assume he works for Mindfire, it's about their level) clearly felt that it spoke for itself. And boy, does it ever! This, ladies-n-gentlemen, is a Prime Number generator according to the author. So...I tried it... According to this code, the prime numbers under 26 are:

            1
            2
            3
            5
            7
            9
            11
            13
            15
            17
            19
            21
            23
            25

            Now, call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3, and both 15 and 25 were divisible by 5... So which is wrong? The Code? Or the Laws of Mathematics? Only the author can tell... :laugh:

            Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

            N Offline
            N Offline
            newton saber
            wrote on last edited by
            #5

            All odd numbers are prime, right? Let me check. Yep, all odd numbers are prime. Makes it a lot easier to count by the primes. Also, are there more odd numbers or even numbers? I know the answer, but it's a puzzle for you.

            I OriginalGriffO P 3 Replies Last reply
            0
            • N newton saber

              All odd numbers are prime, right? Let me check. Yep, all odd numbers are prime. Makes it a lot easier to count by the primes. Also, are there more odd numbers or even numbers? I know the answer, but it's a puzzle for you.

              I Offline
              I Offline
              Ian Shlasko
              wrote on last edited by
              #6

              newton.saber wrote:

              Also, are there more odd numbers or even numbers? I know the answer, but it's a puzzle for you.

              I dunno, let's find out... You start naming odd numbers, and I'll start naming even numbers... Whoever can name more of them wins! :laugh: By the way, is Infinity odd or even? I mean, it's a sideways 8, and 8 is even... But since it's sideways, that's a little odd, right? It's also kind of a car, except they spell it oddly, so maybe the original spelling is even... My head hurts...

              Proud to have finally moved to the A-Ark. Which one are you in?
              Author of the Guardians Saga (Sci-Fi/Fantasy novels)

              D 1 Reply Last reply
              0
              • N newton saber

                All odd numbers are prime, right? Let me check. Yep, all odd numbers are prime. Makes it a lot easier to count by the primes. Also, are there more odd numbers or even numbers? I know the answer, but it's a puzzle for you.

                OriginalGriffO Offline
                OriginalGriffO Offline
                OriginalGriff
                wrote on last edited by
                #7

                newton.saber wrote:

                it's a puzzle for you.

                Not really: there are an infinite quantity of each. The way we define "more", "less", and "equal" for infinite quantities is as follows. For two collections A and B (say A are the even numbers and B are the odd numbers) we say that If you can associate every item in A with a unique item in B, and vice versa, then A and B are the same size. If you can associate every item in A with a unique item in B, but not vice versa, then B is bigger than A. If you can associate every item in B with a unique item in A, but not vice versa, then A is bigger than B. In this case you can associate every even number n with the odd number n+1, and you can associate every odd number m with the even number m−1 (assuming 0 is even) so therefore there are just as many odd numbers as even numbers.

                Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
                "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

                N 1 Reply Last reply
                0
                • I Ian Shlasko

                  newton.saber wrote:

                  Also, are there more odd numbers or even numbers? I know the answer, but it's a puzzle for you.

                  I dunno, let's find out... You start naming odd numbers, and I'll start naming even numbers... Whoever can name more of them wins! :laugh: By the way, is Infinity odd or even? I mean, it's a sideways 8, and 8 is even... But since it's sideways, that's a little odd, right? It's also kind of a car, except they spell it oddly, so maybe the original spelling is even... My head hurts...

                  Proud to have finally moved to the A-Ark. Which one are you in?
                  Author of the Guardians Saga (Sci-Fi/Fantasy novels)

                  D Offline
                  D Offline
                  den2k88
                  wrote on last edited by
                  #8

                  Quote:

                  By the way, is Infinity odd or even? I mean, it's a sideways 8, and 8 is even... But since it's sideways, that's a little odd, right?

                  Please, stop! You're hurting me! :-D

                  1 Reply Last reply
                  0
                  • N newton saber

                    All odd numbers are prime, right? Let me check. Yep, all odd numbers are prime. Makes it a lot easier to count by the primes. Also, are there more odd numbers or even numbers? I know the answer, but it's a puzzle for you.

                    P Offline
                    P Offline
                    PIEBALDconsult
                    wrote on last edited by
                    #9

                    newton.saber wrote:

                    All odd numbers are prime, right?

                    No, primes aren't just any odd number.

                    N 1 Reply Last reply
                    0
                    • Z ZurdoDev

                      OriginalGriff wrote:

                      call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3

                      Ya, but that's also back when Pluto was a planet. We live in a very different place now. This user submitted this in QA, got closed, and resubmitted it in QA. I told him to post as a tip but apparently he didn't realize some explanation should be added. Or, the important part, THAT IT SHOULD WORK! :laugh:

                      There are only 10 types of people in the world, those who understand binary and those who don't.

                      D Offline
                      D Offline
                      DaveAuld
                      wrote on last edited by
                      #10

                      RyanDev wrote:

                      but that's also back when Pluto was a planet

                      There was a thing on the telly recently that stated it had been voted back in as a planet.

                      Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

                      Z P N 3 Replies Last reply
                      0
                      • D DaveAuld

                        RyanDev wrote:

                        but that's also back when Pluto was a planet

                        There was a thing on the telly recently that stated it had been voted back in as a planet.

                        Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

                        Z Offline
                        Z Offline
                        ZurdoDev
                        wrote on last edited by
                        #11

                        True fans never gave up hope. :thumbsup::thumbsup:

                        There are only 10 types of people in the world, those who understand binary and those who don't.

                        1 Reply Last reply
                        0
                        • OriginalGriffO OriginalGriff

                          This is the whole of a would-be Tip submitted today:

                          public class Class1
                          {
                          static void Main(string[] args)
                          {
                          Console.WriteLine("Enter a Number");
                          int num = int.Parse(Console.ReadLine());
                          for (int i = 1; i <=num ; i++)
                          {
                          if(i==2)
                          Console.WriteLine(2);

                                      if (i % 2 != 0)
                                      {
                                          Console.WriteLine(i);
                                      }
                                  }
                          
                               }
                          }
                          

                          No text, no explanation - the author (I can only assume he works for Mindfire, it's about their level) clearly felt that it spoke for itself. And boy, does it ever! This, ladies-n-gentlemen, is a Prime Number generator according to the author. So...I tried it... According to this code, the prime numbers under 26 are:

                          1
                          2
                          3
                          5
                          7
                          9
                          11
                          13
                          15
                          17
                          19
                          21
                          23
                          25

                          Now, call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3, and both 15 and 25 were divisible by 5... So which is wrong? The Code? Or the Laws of Mathematics? Only the author can tell... :laugh:

                          Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                          P Offline
                          P Offline
                          PIEBALDconsult
                          wrote on last edited by
                          #12

                          At least he used the % operator rather than implementing his own function.

                          OriginalGriffO I 2 Replies Last reply
                          0
                          • P PIEBALDconsult

                            At least he used the % operator rather than implementing his own function.

                            OriginalGriffO Offline
                            OriginalGriffO Offline
                            OriginalGriff
                            wrote on last edited by
                            #13

                            I suspect luck was involved.

                            Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                            "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
                            "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

                            1 Reply Last reply
                            0
                            • P PIEBALDconsult

                              At least he used the % operator rather than implementing his own function.

                              I Offline
                              I Offline
                              Ian Shlasko
                              wrote on last edited by
                              #14

                              Yeah, it could have been worse...

                              public static bool SeeIfNumberIsOdd(int i)
                              {
                              for (int n = i; n > 0; n--)
                              {
                              if (n==1)
                              return true;
                              else if (n==2)
                              return false;
                              }
                              return true;
                              }

                              That felt dirty to write... Ok, I probably could have made it a LITTLE worse... Maybe O(n^2), but that might be gratuitous.

                              Proud to have finally moved to the A-Ark. Which one are you in?
                              Author of the Guardians Saga (Sci-Fi/Fantasy novels)

                              P 1 Reply Last reply
                              0
                              • I Ian Shlasko

                                Yeah, it could have been worse...

                                public static bool SeeIfNumberIsOdd(int i)
                                {
                                for (int n = i; n > 0; n--)
                                {
                                if (n==1)
                                return true;
                                else if (n==2)
                                return false;
                                }
                                return true;
                                }

                                That felt dirty to write... Ok, I probably could have made it a LITTLE worse... Maybe O(n^2), but that might be gratuitous.

                                Proud to have finally moved to the A-Ark. Which one are you in?
                                Author of the Guardians Saga (Sci-Fi/Fantasy novels)

                                P Offline
                                P Offline
                                PIEBALDconsult
                                wrote on last edited by
                                #15

                                See the mod function in here: http://www.codeproject.com/script/Articles/ArticleVersion.aspx?aid=830657[^]

                                I 1 Reply Last reply
                                0
                                • P PIEBALDconsult

                                  See the mod function in here: http://www.codeproject.com/script/Articles/ArticleVersion.aspx?aid=830657[^]

                                  I Offline
                                  I Offline
                                  Ian Shlasko
                                  wrote on last edited by
                                  #16

                                  Bah, I can do better than that!

                                  //TODO: Remove all comments before publishing. Real programmers don't need comments!
                                  public function SuperMod(int n, int o) // o is a great variable, because it looks like a zero
                                  {
                                  int p = o; //Shorter variable names make the code run faster!
                                  loopy: //Labels make me feel young again!
                                  while (p < n) p += o;
                                  if (p < n) goto loopy; //Just in case the compiler makes a mistake
                                  int answer = p - n;
                                  return answer;
                                  }

                                  Ok, I think that's about as bad as I can make it, and though I didn't test it at all (Honestly, I think the compiler would come to life and slit my throat for even trying to execute this monstrosity), that should technically give the right answer... Unless 'o' is negative or zero, but validating parameters is so 20th century...

                                  Proud to have finally moved to the A-Ark. Which one are you in?
                                  Author of the Guardians Saga (Sci-Fi/Fantasy novels)

                                  P B 2 Replies Last reply
                                  0
                                  • I Ian Shlasko

                                    Bah, I can do better than that!

                                    //TODO: Remove all comments before publishing. Real programmers don't need comments!
                                    public function SuperMod(int n, int o) // o is a great variable, because it looks like a zero
                                    {
                                    int p = o; //Shorter variable names make the code run faster!
                                    loopy: //Labels make me feel young again!
                                    while (p < n) p += o;
                                    if (p < n) goto loopy; //Just in case the compiler makes a mistake
                                    int answer = p - n;
                                    return answer;
                                    }

                                    Ok, I think that's about as bad as I can make it, and though I didn't test it at all (Honestly, I think the compiler would come to life and slit my throat for even trying to execute this monstrosity), that should technically give the right answer... Unless 'o' is negative or zero, but validating parameters is so 20th century...

                                    Proud to have finally moved to the A-Ark. Which one are you in?
                                    Author of the Guardians Saga (Sci-Fi/Fantasy novels)

                                    P Offline
                                    P Offline
                                    PIEBALDconsult
                                    wrote on last edited by
                                    #17

                                    Ian Shlasko wrote:

                                    give the right an answer

                                    FTFY

                                    I 1 Reply Last reply
                                    0
                                    • P PIEBALDconsult

                                      newton.saber wrote:

                                      All odd numbers are prime, right?

                                      No, primes aren't just any odd number.

                                      N Offline
                                      N Offline
                                      newton saber
                                      wrote on last edited by
                                      #18

                                      PIEBALDconsult wrote:

                                      No, primes aren't just any odd number.

                                      Of course they are. It's ridiculous to think that they aren't.

                                      1 Reply Last reply
                                      0
                                      • OriginalGriffO OriginalGriff

                                        newton.saber wrote:

                                        it's a puzzle for you.

                                        Not really: there are an infinite quantity of each. The way we define "more", "less", and "equal" for infinite quantities is as follows. For two collections A and B (say A are the even numbers and B are the odd numbers) we say that If you can associate every item in A with a unique item in B, and vice versa, then A and B are the same size. If you can associate every item in A with a unique item in B, but not vice versa, then B is bigger than A. If you can associate every item in B with a unique item in A, but not vice versa, then A is bigger than B. In this case you can associate every even number n with the odd number n+1, and you can associate every odd number m with the even number m−1 (assuming 0 is even) so therefore there are just as many odd numbers as even numbers.

                                        Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                                        N Offline
                                        N Offline
                                        newton saber
                                        wrote on last edited by
                                        #19

                                        This is terribly incorrect, because I stopped counting on an odd number, so there are more odd numbers than even. Thank you for your input. :D

                                        P 1 Reply Last reply
                                        0
                                        • OriginalGriffO OriginalGriff

                                          This is the whole of a would-be Tip submitted today:

                                          public class Class1
                                          {
                                          static void Main(string[] args)
                                          {
                                          Console.WriteLine("Enter a Number");
                                          int num = int.Parse(Console.ReadLine());
                                          for (int i = 1; i <=num ; i++)
                                          {
                                          if(i==2)
                                          Console.WriteLine(2);

                                                      if (i % 2 != 0)
                                                      {
                                                          Console.WriteLine(i);
                                                      }
                                                  }
                                          
                                               }
                                          }
                                          

                                          No text, no explanation - the author (I can only assume he works for Mindfire, it's about their level) clearly felt that it spoke for itself. And boy, does it ever! This, ladies-n-gentlemen, is a Prime Number generator according to the author. So...I tried it... According to this code, the prime numbers under 26 are:

                                          1
                                          2
                                          3
                                          5
                                          7
                                          9
                                          11
                                          13
                                          15
                                          17
                                          19
                                          21
                                          23
                                          25

                                          Now, call me old fashioned, but in my day, 9, 15 and 21 were divisible by 3, and both 15 and 25 were divisible by 5... So which is wrong? The Code? Or the Laws of Mathematics? Only the author can tell... :laugh:

                                          Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                                          P Offline
                                          P Offline
                                          PIEBALDconsult
                                          wrote on last edited by
                                          #20

                                          http://www.codeproject.com/Lounge.aspx?msg=85311#xx85311xx[^] http://www.codeproject.com/search.aspx?q=prime+number+error&categoryid=f1_1159_[^]

                                          1 Reply Last reply
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