operator << method
Shift the bits of this integer to the left by shiftAmount.
Shifting to the left makes the number larger, effectively multiplying
the number by pow(2, shiftIndex).
There is no limit on the size of the result. It may be relevant to limit intermediate values by using the "and" operator with a suitable mask.
It is an error if shiftAmount is negative.
Implementation
BigInt operator <<(int shiftAmount);