Data commit

Task/Negative-base-numbers/FreeBASIC/negative-base-numbers.basic

@@ -0,0 +1,75 @@
+#define DIGITS  "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+Dim cadena(63) As String
+
+Function mod2(a As Long, b As Integer) As Long
+    Return a - (a \ b) * b
+End Function
+
+Function StrReverse(Byval text As String) As String
+    Dim As String text2 = text
+    Dim As Integer x, lt = Len(text)
+
+    For x = 0 To lt Shr 1 - 1
+        Swap text2[x], text2[lt - x - 1]
+    Next x
+    Return text2
+End Function
+
+Function EncodeNegativeBase(Byval n As Long, base_ As Integer) As String
+    Dim As Long Puntero, idx, rem_
+    Dim result As String
+
+    If base_ > -1 Or base_ < -62 Then
+        Return result
+    Else
+        If n = 0 Then
+            Return "0"
+        Else
+            Puntero = 0
+            Do While n <> 0
+                rem_ = mod2(n, base_)
+                n \= base_
+                If rem_ < 0 Then
+                    n += 1
+                    rem_ = rem_ - base_
+                End If
+                result &= Mid(DIGITS, rem_ + 1, 1)
+            Loop
+        End If
+    End If
+    Return StrReverse(result)
+End Function
+
+Function DecodeNegativeBase(ns As String, base_ As Integer) As Long
+    Dim As Long total, bb
+    Dim As Integer i, j
+
+    If base_ < -62 Or base_ > -1 Then Return 0
+    If Mid(ns, 1, 1) = "0" Or (Mid(ns, 1, 1) = "0" And Mid(ns, 2, 1) = "0") Then Return 0
+    i = Len(ns)
+    total = 0
+    bb = 1
+    Do While i >= 1
+        j = Instr(DIGITS, Mid(ns, i, 1)) - 1
+        total += j * bb
+        bb *= base_
+        i -= 1
+    Loop
+    Return total
+End Function
+
+Sub Driver(n As Long, b As Integer)
+    Dim As String ns = EncodeNegativeBase(n, b)
+    Print Str(n); " encoded in base "; b; " = "; ns
+    Dim As Long p = DecodeNegativeBase(ns, b)
+    Print ns; " decoded in base "; b; " ="; p
+    Print
+End Sub
+
+Driver 10, -2
+Driver 146, -3
+Driver 15, -10
+Driver 118492, -62
+
+Sleep