Left shift (<<)

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left shift operator ( << ) shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded. Zero bits are shifted in from the right.

a << b

描述

This operator shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded. Zero bits are shifted in from the right.

.    9 (base 10): 00000000000000000000000000001001 (base 2)
--------------------------------
9 << 2 (base 10): 00000000000000000000000000100100 (base 2) = 36 (base 10)

Bitwise shifting any number x to the left by y bits yields x * 2 ** y .
So e.g.: 9 << 3 translates to: 9 * (2 ** 3) = 9 * (8) = 72 .

范例

Using left shift

9 << 3; // 72
// 9 * (2 ** 3) = 9 * (8) = 72

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