The Weird and The Wonderful

mav.northwind wrote:

1 is not a prime number, by definition.

dbrenth wrote:

The first 10000 prime numbers[^]

Giorgi Dalakishvili wrote:

Ask him to write a function that returns weather or not a given number is even

PIEBALDconsult wrote:

Wouldn't this be a good Friday programming quiz?

int Primes[]={2,3,5,7,...,113};
int size=sizeof(Primes[])/sizeof(Primes[0]);
int i=0;
while (i<size)
{
  if (num==Primes[i]) return true;
}
return false;

int Primes[]={2,3,5,7,...,113};
int size=sizeof(Primes[])/sizeof(Primes[0]);
int i=0;
while (i<size)
{
  if (num==Primes[i]) return true;
}
return false;

int primes[] = {2,3,5,...133};
const int* end = primes + sizeof(primes)/sizeof(int);
return (std::find(primes, end, num) != end);

bool IsPrime(int i)
{
  if (i<2)
    return false;
  if (i == 2)
    return true;
  if (i%2 == 1)
    // All odd numbers are prime:
    // 3 ... prime
    // 5 ... prime
    // 7 ... prime
    // 9 ... measuring fault
    // 11... prime
    // 13... prime
    // and so on...
    return true;
  else
    return false;
}

public static partial class NumberKeeper
{
    [System.FlagsAttribute]
    public enum NumberProperty
    {
        None       =   0
    ,
        Odd        =   1
    ,
        Even       =   2
    ,
        Positive   =   4
    ,
        Negative   =   8
    ,
        Prime      =  16
    ,
        PowerOfTwo =  32
    ,
        Square     =  64
    ,
        Cube       = 128
    ,
        Fibonacci  = 256
    ,
        Factorial  = 512

        /* et cetera */
    } ;

    public static readonly System.Collections.Generic.Dictionary<int,NumberProperty> Numbers ;

    static NumberKeeper
    (
    )
    {
        Numbers = new System.Collections.Generic.Dictionary<int,NumberProperty>() ;

        Numbers.Add (   0 , NumberProperty.None ) ;
        Numbers.Add (   1 , NumberProperty.Odd  | NumberProperty.Positive                         | NumberProperty.PowerOfTwo | NumberProperty.Fibonacci | NumberProperty.Factorial ) ;
        Numbers.Add (   2 , NumberProperty.Even | NumberProperty.Positive | NumberProperty.Prime  | NumberProperty.PowerOfTwo | NumberProperty.Fibonacci | NumberProperty.Factorial ) ;
        Numbers.Add (   3 , NumberProperty.Odd  | NumberProperty.Positive | NumberProperty.Prime                              | NumberProperty.Fibonacci ) ;
        Numbers.Add (   4 , NumberProperty.Even | NumberProperty.Positive | NumberProperty.Square | NumberProperty.PowerOfTwo ) ;
        Numbers.Add (   5 , NumberProperty.Odd  | NumberProperty.Positive | NumberProperty.Prime                              | NumberProperty.Fibonacci ) ;
        Numbers.Add (   6 , NumberProperty.Even | NumberProperty.Positive                                                                                | NumberProperty.Factorial ) ;
        Numbers.Add (   7 , NumberProperty.Odd  | NumberProperty.Positive | NumberProperty.Prime  ) ;
        Numbers.Add (   8 , NumberProperty.Even | NumberProperty.Positive | NumberProperty.Cube   | NumberProperty.PowerOfTwo | NumberProperty.Fibonacci ) ;
        Numbers.Add (   9 , NumberProperty.Odd  | NumberProperty.Positive | NumberProperty.Square ) ;
        Numbers.Add (  10 , NumberProperty.Even | NumberProperty.Positive ) ;
        Numbers.Add (  -1 , NumberProperty.Odd  | NumberProperty.Negative ) ;
        Numbers.Add (  -2 , NumberProperty.Even | NumberProperty.Negative ) ;
        Numbers.Add (  -3 , NumberProperty.Odd  | NumberProperty.Negative ) ;
        Numbers.Add (  -4 , NumberProperty.Even | NumberProperty.Negative ) ;
        Numbers.Add (  -5 , NumberProperty.Odd  | NumberProperty.Negative ) ;
        Numbers.Add (  -6 , NumberProperty.Even | NumberProperty.Negative ) ;
        Numbers.Add (  -7 , NumberProperty.Odd  | NumberProperty.Negative ) ;
        Numbers.Add (  -8 , NumberProperty.Even | NumberProperty.Negative | NumberProperty.Cube   ) ;
        Numbers.Add (  -9 , NumberProperty.Odd  | NumberProperty.Negative ) ;
        Numbers.Add ( -10 , NumberProperty.Even | NumberProperty.Negative ) ;

        /* et cetera */

        return ;
    }

    private static bool
    HasProperty
    (
        int            Subject
    ,
        NumberProperty Property
    )
    {
        return ( Numbers.ContainsKey ( Subject ) && ( ( Numbers [ Subject ] & Property ) == Property ) ) ;
    }

    public static bool
    IsPrime
    (
        int Subject
    )
    {
        return ( HasProperty ( Subject , NumberProperty.Prime ) ) ;
    }

    /* et cetera */

}