excel vba bitshift right
'Many languages have a bitwise signed-right-shift operator: >> 'VBA does not. However, it can be emulated in a performant manner: Dim n as Long n = 6 n = (n And -2) \ 2 '1 signed-right-shift (6 >> 1) = 3 n = 8 n = (n And -4) \ 4 '2 signed-right-shifts (8 >> 2) = 2 n = 170 n = (n And -8) \ 8 '3 signed-right-shifts (170 >> 3) = 21 n = -170 n = (n And -16) \ 16 '4 signed-right-shifts (-170 >> 4) = -11 'Notice the pattern: 'n = (n And -2^shfits) \ 2^shifts 'Important: Exponentiation is SLOW. It is much faster to use the hard coded ' result of the exponentiation, as in the examples above. n = -2023406815 n = (n And -16777216) \ 16777216 '24 signed-right-shifts (-2023406815 >> 24) = -121 'Imporatant: Since a Long Integer in VBA is signed, (n >> 31) needs special 'processing. The pattern is different: n = 2147483647 n = n And -2147483648 '31 signed-right-shifts (-2147483647 >> 31) = 0 'Here is a VBA function that encapsulates the details: Function ShiftRight&(ByVal n&, Optional ByVal shifts& = 1) Dim d& Select Case shifts Case 1: d = 2& Case 2: d = 4& Case 3: d = 8& Case 4: d = 16& Case 5: d = 32& Case 6: d = 64& Case 7: d = 128& Case 8: d = 256& Case 9: d = 512& Case 10: d = 1024& Case 11: d = 2048& Case 12: d = 4096& Case 13: d = 8192& Case 14: d = 16384& Case 15: d = 32768 Case 16: d = 65536 Case 17: d = 131072 Case 18: d = 262144 Case 19: d = 524288 Case 20: d = 1048576 Case 21: d = 2097152 Case 22: d = 4194304 Case 23: d = 8388608 Case 24: d = 16777216 Case 25: d = 33554432 Case 26: d = 67108864 Case 27: d = 134217728 Case 28: d = 268435456 Case 29: d = 536870912 Case 30: d = 1073741824 Case 31: ShiftRight = CBool(n And &H80000000): Exit Function Case 0: ShiftRight = n: Exit Function End Select ShiftRight = (n And -d) \ d End Function 'Don't be off-put at the size of the function. This is many times faster than 'any other VBA function that carries out bitwise signed-right-shfits. It is 'thousands of times faster than calling Excel's 'WorksheetFunction.Bitrshift() method. 'However, remember that function calls are expensive in general. The inline 'examples above are approximately 20 times faster than calling this highly 'optimized function. But you have to get the math right. The function 'takes care of it for you.