Prime Numbers in Visual Basic QuickStart Sample

Illustrates working with prime numbers and the IntegerMath class in the Numerics.NET namespace in Visual Basic.

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Option Infer On

' We use classes from the Numerics.NET.SpecialFunctions 
' namespace.
Imports Numerics.NET

' Illustrates working with prime numbers using the 
' IntegerMath class in the Numerics.NET.SpecialFunctions 
' namespace of Numerics.NET.
Module PrimeNumbers
    Sub Main()
        ' The license is verified at runtime. We're using
        ' a 30 day trial key here. For more information, see
        '     https://numerics.net/trial-key
        Numerics.NET.License.Verify("64542-18980-57619-62268")

        '
        ' Factoring numbers
        '

        ' The Factor method returns a sequence of pairs of the prime factors
        ' and their multiplicity:
        Dim index As Integer
        Dim n As Integer = 1001110110
        Dim factors As Integer() = IntegerMath.Factor(n)

        Console.Write("{0} = {1}", n, factors(0))
        For index = 1 To factors.Length - 1
            Console.Write(" * {0}", factors(index))
        Next
        Console.WriteLine()

        ' Factors that occur multiple times is repeated as many times as necessary:
        n = 256 * 6157413
        factors = IntegerMath.Factor(n)
        Console.Write("{0} = {1}", n, factors(0))
        For index = 1 To factors.Length - 1
            Console.Write(" * {0}", factors(index))
        Next
        Console.WriteLine()

        ' The 64bit version can safely factor numbers up to 48 bits long:
        Dim n2 As long = 1296523 * 1177157L
        Dim factors2 As long() = IntegerMath.Factor(n2)
        Console.Write("{0} = {1}", n2, factors2(0))
        For index = 1 To factors2.Length - 1
            Console.Write(" * {0}", factors2(index))
        Next
        Console.WriteLine()

        ' Let's try a longer number
        n2 = 4292017459171704241
        factors2 = IntegerMath.Factor(n2)
        Console.Write("{0} = {1}", n2, factors2(0))
        For index = 1 To factors2.Length - 1
            Console.Write(" * {0}", factors2(index))
        Next
        Console.WriteLine()

        '
        ' Prime numbers
        '

        ' The IsPrime method verifies if a number is prime or not.
        n = 801853937
        Console.WriteLine("{0} is prime? {1}!", n, IntegerMath.IsPrime(n))
        n = 801853939
        Console.WriteLine("{0} is prime? {1}!", n, IntegerMath.IsPrime(n))

        ' MextPrime gets the first prime after a specified number. 
        ' You can call it repeatedly to get successive primes.
        ' Let's get the 10 smallest primes larger than one billion:
        Console.WriteLine("First 10 primes greater than 1 billion:")
        n = 1000000000
        For index = 1 To 10
            n = IntegerMath.NextPrime(n)
            Console.Write("{0,16}", n)
        Next
        Console.WriteLine()

        ' PreviousPrime gets the last prime before a specified number. 
        Console.WriteLine("Last 10 primes less than 1 billion:")
        n = 1000000000
        For index = 1 To 10
            n = IntegerMath.PreviousPrime(n)
            Console.Write("{0,16}", n)
        Next
        Console.WriteLine()

        Console.Write("Press Enter key to exit...")
        Console.ReadLine()
    End Sub

End Module