Source code in the freebasic programming language

' version 21-10-2016
' compile with: fbc -s console
' for boundry checks on array's compile with: fbc -s console -exx

Sub cocktailsort(bs() As Long)
    ' sort from lower bound to the highter bound
    ' array's can have subscript range from -2147483648 to +2147483647
    Dim As Long lb = LBound(bs)
    Dim As Long ub = UBound(bs) -1
    Dim As Long done, i

    Do
        done = 0                  ' going up
        For i = lb To ub
            If bs(i) > bs(i +1) Then
                Swap bs(i), bs(i +1)
                done = 1
            End If
        Next
        ub = ub -1
        If done = 0 Then Exit Do  ' 0 means the array is sorted
        done = 0                  ' going down
        For i = ub To lb Step -1
            If bs(i) > bs(i +1) Then
                Swap bs(i), bs(i +1)
                done = 1
            End If
        Next
        lb = lb +1
    Loop Until done = 0           ' 0 means the array is sorted

End Sub

' ------=< MAIN >=------

Dim As Long i, array(-7 To 7)

Dim As Long a = LBound(array), b = UBound(array)

Randomize Timer
For i = a To b : array(i) = i  : Next
For i = a To b ' little shuffle
    Swap array(i), array(Int(Rnd * (b - a +1)) + a)
Next


Print "unsorted ";
For i = a To b : Print Using "####"; array(i); : Next : Print
cocktailsort(array())  ' sort the array
Print "  sorted ";
For i = a To b : Print Using "####"; array(i); : Next : Print


' empty keyboard buffer
While Inkey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End