not - logical not operator.
bool not -> bool
int not -> int
1 2 eq not -> true
0 not -> -1
For booleans, not turns true info false and vice versa.
For integer arguments, not performs a bit-wise not where
1 is replaced by 0 and vice versa.
/builddir/build/BUILD/nest-simulator-3.3/nest-simulator-3.3/sli/slimath.cc