Answers for "vba <<"

excel vba bitshift left

'Many programming languages have a bitwise left-shift operator: <<
'VBA does not. However, it can be emulated in a performant function:

Function ShiftLeft1&(ByVal n&)
    ShiftLeft1 = 2& * (n And 1073741823): If n And 1073741824 Then ShiftLeft1 = ShiftLeft1 Or &H80000000
End Function
  
MsgBox ShiftLeft1(170)    '<--displays 340      1 left-shift (170 << 1) = 340
  
'-------------------------------------------------------------------------------------------------------  

Function ShiftLeft2&(ByVal n&)
    ShiftLeft2 = 4& * (n And 536870911): If n And 536870912 Then ShiftLeft2 = ShiftLeft2 Or &H80000000
End Function
  
MsgBox ShiftLeft2(170)    '<--displays 680      2 left-shift3 (170 << 2) = 680
  
'-------------------------------------------------------------------------------------------------------  

Function ShiftLeft3&(ByVal n&)
    ShiftLeft3 = 8& * (n And 268435455): If n And 268435456 Then ShiftLeft3 = ShiftLeft3 Or &H80000000
End Function
  
MsgBox ShiftLeft3(170)    '<--displays 1360     3 left-shifts (170 << 3) = 1360
  
'-------------------------------------------------------------------------------------------------------  

Function ShiftLeft4&(ByVal n&)
    ShiftLeft4 = 16& * (n And 134217727): If n And 134217728 Then ShiftLeft4 = ShiftLeft4 Or &H80000000
End Function
  
MsgBox ShiftLeft4(170)    '<--displays 2720     4 left-shifts (170 << 4) = 2720
  
'NB: Thses function are extremely fast. But they are hard-coded for predefined number of place shifts.
'    Here is a generic function that handles all 31 possible place shifts:
        
Function ShiftLeft&(ByVal n&, Optional ByVal shifts& = 1)
    Dim d&
    Select Case shifts
        Case 1:  d = 2& * (n And 1073741823): If n And 1073741824 Then d = d Or &H80000000
        Case 2:  d = 4& * (n And 536870911):  If n And 536870912 Then d = d Or &H80000000
        Case 3:  d = 8& * (n And 268435455):  If n And 268435456 Then d = d Or &H80000000
        Case 4:  d = 16& * (n And 134217727): If n And 134217728 Then d = d Or &H80000000
        Case 5:  d = 32& * (n And 67108863):  If n And 67108864 Then d = d Or &H80000000
        Case 6:  d = 64& * (n And 33554431):  If n And 33554432 Then d = d Or &H80000000
        Case 7:  d = 128& * (n And 16777215): If n And 16777216 Then d = d Or &H80000000
        Case 8:  d = 256& * (n And 8388607):  If n And 8388608 Then d = d Or &H80000000
        Case 9:  d = 512& * (n And 4194303):  If n And 4194304 Then d = d Or &H80000000
        Case 10: d = 1024& * (n And 2097151): If n And 2097152 Then d = d Or &H80000000
        Case 11: d = 2048& * (n And 1048575): If n And 1048576 Then d = d Or &H80000000
        Case 12: d = 4096& * (n And 524287):  If n And 524288 Then d = d Or &H80000000
        Case 13: d = 8192& * (n And 262143):  If n And 262144 Then d = d Or &H80000000
        Case 14: d = 16384& * (n And 131071): If n And 131072 Then d = d Or &H80000000
        Case 15: d = 32768 * (n And 65535):   If n And 65536 Then d = d Or &H80000000
        Case 16: d = 65536 * (n And 32767&):  If n And 32768 Then d = d Or &H80000000
        Case 17: d = 131072 * (n And 16383&): If n And 16384& Then d = d Or &H80000000
        Case 18: d = 262144 * (n And 8191&):  If n And 8192& Then d = d Or &H80000000
        Case 19: d = 524288 * (n And 4095&):  If n And 4096& Then d = d Or &H80000000
        Case 20: d = 1048576 * (n And 2047&): If n And 2048& Then d = d Or &H80000000
        Case 21: d = 2097152 * (n And 1023&): If n And 1024& Then d = d Or &H80000000
        Case 22: d = 4194304 * (n And 511&):  If n And 512& Then d = d Or &H80000000
        Case 23: d = 8388608 * (n And 255&):  If n And 256& Then d = d Or &H80000000
        Case 24: d = 16777216 * (n And 127&): If n And 128& Then d = d Or &H80000000
        Case 25: d = 33554432 * (n And 63&):  If n And 64& Then d = d Or &H80000000
        Case 26: d = 67108864 * (n And 31&):  If n And 32& Then d = d Or &H80000000
        Case 27: d = 134217728 * (n And 15&): If n And 16& Then d = d Or &H80000000
        Case 28: d = 268435456 * (n And 7&):  If n And 8& Then d = d Or &H80000000
        Case 29: d = 536870912 * (n And 3&):  If n And 4& Then d = d Or &H80000000
        Case 30: d = 1073741824 * (n And 1&): If n And 2& Then d = d Or &H80000000
        Case 31: If n And &H1& Then d = &H80000000 Else d = &H0&
        Case 0:  d = n
    End Select
    ShiftLeft = d
End Function

MsgBox ShiftLeft(1, 24) '<--displays 16777216     24 left-shifts (1 << 24) = 16777216

                                                                      
'NB: Remember that VBA Longs are signed.