cross product for 3 dimension vector
init quantum.hpp
move code form spin.hpp
fix namespace and hbar
move to namespace Tensor
add spin.hpp
add unary + and -
include cmath for M_PI
add variadic parameter prod
add vector operator S
set default scalar type to double
add identity tensor
add variadic parameter dot
double is no longer default scalar
new length literal constant
Operator(int) become explicit
small fix: 0 => scalar(0)
add abs(vector)
fix type for abs
remove default dim for I and O