Minus of a variable in C++?

Question

I have this equation:

R= 2*(-I dot N)*N + I

Can I simply type (-I) or something similar, or do I have to multiply I by -1?

Answer 1

C++ has a unary minus operator that performs negation.

- x

This negates x, just like 0 - x or -1 * x would negate x. Note that the - in -1 * x is also the unary minus operator.

Answer 2

You mention in your comment that:

I is a direction vector

If you're using operators on non-native types, you can't assume that they are defined. It depends whether operator overloading has been implemented on the class: if there is a Vector Vector operator-() member function

Also, mathematically speaking, (-I dot N) == -(I dot N) :)