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<< Operator

Performs an arithmetic left shift on a bit pattern.

result = pattern << amount

Parts

result
Required. Integral numeric value. The result of shifting the bit pattern. The data type is the same as that of pattern.
pattern
Required. Integral numeric expression. The bit pattern to be shifted. The data type must be Byte, Short, Integer, or Long.
amount
Required. Numeric expression. The number of bits to shift the bit pattern. The data type must be Integer or widen to Integer.

Remarks

Arithmetic shifts are not circular, which means the bits shifted off one end of the result are not reintroduced at the other end. In an arithmetic left shift, the bits shifted beyond the range of the result data type are discarded, and the bit positions vacated on the right are set to zero.

To prevent shifting by more bits than the result can hold, Visual Basic masks the value of amount with a size mask corresponding to the data type of pattern. The binary AND of these values is used for the shift amount. The size masks are as follows:

Data type of pattern Size mask (decimal) Size mask (hexadecimal)
Byte 7 &H00000007
Short 15 &H0000000F
Integer 31 &H0000001F
Long 63 &H0000003F

If amount is zero, the value of result is identical to the value of pattern. If amount is negative, it is taken as an unsigned value and masked with the appropriate size mask.

Arithmetic shifts never generate overflow exceptions.

Example

This example uses the << operator to perform arithmetic left shifts on integral values. The result always has the same data type as that of the expression being shifted.

Dim Pattern As Short = 192   ' Bit pattern is 0000 0000 1100 0000.
Dim Result1, Result2, Result3, Result4, Result5 As Short
Result1 = Pattern << 0      ' Result is 192 (0000 0000 1100 0000).
Result2 = Pattern << 4     ' Result is 3072 (0000 1100 0000 0000).
Result3 = Pattern << 9   ' Result is -32768 (1000 0000 0000 0000).
Result4 = Pattern << 17     ' Result is 384 (0000 0001 1000 0000).
Result5 = Pattern << -1   ' Result is 0 (shifted 15 places to left).

The shift amount for Result4 is calculated as 17 AND 15, which equals 1.

See Also

Bit Shift Operators | Assignment Operators | <<= Operator | Operator Precedence in Visual Basic | Operators Listed by Functionality | Arithmetic Operators

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