Operator !! in Kernel C

Question

I encountered the below code in C program.

int a = !! b ;

variable b is also an integer. Initially I thought it is 'not' operator with a typo :)

Can someone help in explaining this?

Answer 1

This is operator !, which is used twice in row. If b is non-zero, a gets value 1, and if b is zero, a gets value 0.