Data commit

Task/Safe-primes-and-unsafe-primes/Visual-Basic-.NET/safe-primes-and-unsafe-primes-1.vb

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+Imports System.Console
+
+Namespace safety
+    Module SafePrimes
+        Dim pri_HS As HashSet(Of Integer) = Primes(10_000_000).ToHashSet()
+
+        Sub Main()
+            For Each UnSafe In {False, True} : Dim n As Integer = If(UnSafe, 40, 35)
+                WriteLine($"The first {n} {If(UnSafe, "un", "")}safe primes are:")
+                WriteLine(String.Join(" ", pri_HS.Where(Function(p) UnSafe Xor
+                                                            pri_HS.Contains(p \ 2)).Take(n)))
+            Next : Dim limit As Integer = 1_000_000 : Do
+                Dim part = pri_HS.TakeWhile(Function(l) l < limit),
+                 sc As Integer = part.Count(Function(p) pri_HS.Contains(p \ 2))
+                WriteLine($"Of the primes below {limit:n0}: {sc:n0} are safe, and {part.Count() -
+                          sc:n0} are unsafe.") : If limit = 1_000_000 Then limit *= 10 Else Exit Do
+            Loop
+        End Sub
+
+        Private Iterator Function Primes(ByVal bound As Integer) As IEnumerable(Of Integer)
+            If bound < 2 Then Return
+            Yield 2
+            Dim composite As BitArray = New BitArray((bound - 1) \ 2)
+            Dim limit As Integer = (CInt((Math.Sqrt(bound))) - 1) \ 2
+            For i As Integer = 0 To limit - 1 : If composite(i) Then Continue For
+                Dim prime As Integer = 2 * i + 3 : Yield prime
+                Dim j As Integer = (prime * prime - 2) \ 2
+                While j < composite.Count : composite(j) = True : j += prime : End While
+            Next
+            For i As integer = limit To composite.Count - 1 : If Not composite(i) Then Yield 2 * i + 3
+            Next
+        End Function
+    End Module
+End Namespace

Task/Safe-primes-and-unsafe-primes/Visual-Basic-.NET/safe-primes-and-unsafe-primes-2.vb

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+Imports System.Runtime.CompilerServices

Task/Safe-primes-and-unsafe-primes/Visual-Basic-.NET/safe-primes-and-unsafe-primes-3.vb

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+    Module Extensions
+        <Extension()>
+        Function ToHashSet(Of T)(ByVal src As IEnumerable(Of T), ByVal Optional _
+                                 IECmp As IEqualityComparer(Of T) = Nothing) As HashSet(Of T)
+            Return New HashSet(Of T)(src, IECmp)
+        End Function
+    End Module