Negative base numbers: Difference between revisions

=={{header|FreeBASIC}}==

{{trans|VBA}}

<syntaxhighlight lang="vb">#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</syntaxhighlight>

{{out}}

<pre>Same as VBA entry.</pre>