Why use a+=b instead of a = a + b in C++?

1. a, b are of same type:

a += b only needs 1 assignment, it’s like [pass by reference]

but for a = a + b, the process is as follows:

temp = a
a = temp + b

it’s take 2 assignment.

when a, b are strings, the problem is especially obvious.

2. a, b are of different types

a += b can do implicit typecasting but a = a + b cannot