Data commit

Task/Isqrt-integer-square-root-of-X/Visual-Basic-.NET/isqrt-integer-square-root-of-x.vb

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+Imports System
+Imports System.Console
+Imports BI = System.Numerics.BigInteger
+
+Module Module1
+    Function isqrt(ByVal x As BI) As BI
+        Dim t As BI, q As BI = 1, r As BI = 0
+        While q <= x : q <<= 2 : End While
+        While q > 1 : q >>= 2 : t = x - r - q : r >>= 1
+            If t >= 0 Then x = t : r += q
+        End While : Return r
+    End Function
+
+    Sub Main()
+        Const max As Integer = 73, smax As Integer = 65
+        Dim power_width As Integer = ((BI.Pow(7, max).ToString().Length \ 3) << 2) + 3,
+            isqrt_width As Integer = (power_width + 1) >> 1,
+            n as Integer
+        WriteLine("Integer square root for numbers 0 to {0}:", smax)
+        For n = 0 To smax : Write("{0} ", (n \ 10).ToString().Replace("0", " "))
+            Next : WriteLine()
+        For n = 0 To smax : Write("{0} ", n Mod 10) : Next : WriteLine()
+        WriteLine(New String("-"c, (smax << 1) + 1))
+        For n = 0 To smax : Write("{0} ", isqrt(n)) : Next
+        WriteLine(vbLf & vbLf & "Integer square roots of odd powers of 7 from 1 to {0}:", max)
+        Dim s As String = String.Format("[0,2] |[1,{0}:n0] |[2,{1}:n0]",
+            power_width, isqrt_width).Replace("[", "{").Replace("]", "}")
+        WriteLine(s, "n", "7 ^ n", "isqrt(7 ^ n)")
+        WriteLine(New String("-"c, power_width + isqrt_width + 6))
+        Dim p As BI = 7 : n = 1 : While n <= max
+            WriteLine(s, n, p, isqrt(p)) : n += 2 : p = p * 49
+        End While
+    End Sub
+End Module