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Bitwise Left Shift Operator (<<) 

Left shifts the bits of an expression.


expression1 << expression2

expression1

Any numeric expression.

expression2

Any numeric expression.

The << operator shifts the bits of expression1 left by the number of bits specified in expression2. The data type of expression1 determines the data type returned by this operator.

The << operator masks expression2 to avoid shifting expression1 by too much. Otherwise, if the shift amount exceeded the number of bits in the data type of expression1, all the original bits would be shifted away to give a trivial result. To ensure that each shift leaves at least one of the original bits, the shift operators use the following formula to calculate the actual shift amount: mask expression2 (using the bitwise AND operator) with one less than the number of bits in expression1.

For example:

var temp
temp = 14 << 2

The variable temp has a value of 56 because 14 (00001110 in binary) shifted left two bits equals 56 (00111000 in binary).

To illustrate how the masking works, consider the following example.

var x : byte = 15;
// A byte stores 8 bits.
// The bits stored in x are 00001111
var y : byte = x << 10;
// Actual shift is 10 & (8-1) = 2
// The bits stored in y are 00111100
// The value of y is 60
print(y); // Prints 60

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