C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

27. Prefer the canonical forms of arithmetic and assignment operators

Summary

If you a+b, also a+=b: When defining binary arithmetic operators, provide their assignment versions as well, and write to minimize duplication and maximize efficiency.

Discussion

In general, for some binary operator @ (be it +, -, *, and so on), you should define its assignment version such that a @= b and a = a @ b have the same meaning (other than that the first form might be more efficient and only evaluates a once). The canonical way of achieving this goal is to define @ in terms of @=, as follows:

The two functions work in tandem. The assignment form does the ...