Data commit

Task/Arbitrary-precision-integers-included-/Visual-Basic-.NET/arbitrary-precision-integers-included-.vb

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+Imports System.Console
+Imports BI = System.Numerics.BigInteger
+
+Module Module1
+
+    Dim Implems() As String = {"Built-In", "Recursive", "Iterative"},
+        powers() As Integer = {5, 4, 3, 2}
+
+    Function intPowR(val As BI, exp As BI) As BI
+        If exp = 0 Then Return 1
+        Dim ne As BI, vs As BI = val * val
+        If exp.IsEven Then ne = exp >> 1 : Return If (ne > 1, intPowR(vs, ne), vs)
+        ne = (exp - 1) >> 1 : Return If (ne > 1, intPowR(vs, ne), vs) * val
+    End Function
+
+    Function intPowI(val As BI, exp As BI) As BI
+        intPowI = 1 : While (exp > 0) : If Not exp.IsEven Then intPowI *= val
+            val *= val : exp >>= 1 : End While
+    End Function
+
+    Sub DoOne(title As String, p() As Integer)
+        Dim st As DateTime = DateTime.Now, res As BI, resStr As String
+        Select Case (Array.IndexOf(Implems, title))
+            Case 0 : res = BI.Pow(p(0), CInt(BI.Pow(p(1), CInt(BI.Pow(p(2), p(3))))))
+            Case 1 : res = intPowR(p(0), intPowR(p(1), intPowR(p(2), p(3))))
+            Case Else : res = intPowI(p(0), intPowI(p(1), intPowI(p(2), p(3))))
+        End Select : resStr = res.ToString()
+        Dim et As TimeSpan = DateTime.Now - st
+        Debug.Assert(resStr.Length = 183231)
+        Debug.Assert(resStr.StartsWith("62060698786608744707"))
+        Debug.Assert(resStr.EndsWith("92256259918212890625"))
+        WriteLine("n = {0}", String.Join("^", powers))
+        WriteLine("n = {0}...{1}", resStr.Substring(0, 20),  resStr.Substring(resStr.Length - 20, 20))
+        WriteLine("n digits = {0}", resStr.Length)
+        WriteLine("{0} elasped: {1} milliseconds." & vblf, title, et.TotalMilliseconds)
+    End Sub
+
+    Sub Main()
+        For Each itm As String in Implems : DoOne(itm, powers) : Next
+        If Debugger.IsAttached Then Console.ReadKey()
+    End Sub
+
+End Module