How do I overload += in Julia?

Question

I'm trying to understand how operator overloading works in Julia. The manual is quite brief, and gives +() as an example function, then states all the operators are overloadable with their obvious names (a list of non-obvious names is also provided).

But what about +=? The function +=() doesn't even seem to exist, nor does +=!() (since it is a modifying function). I frequently overload operators in C++ by defining += first and then use a simple + based on copy and +=.

In my case I don't even think I need +, just the behavior of +=... I realize I could write my own modifying function but the operator syntax would be nice. (Out of curiosity, how do *=, /=, $=, etc work?)

Answer 1

There is no += function. It is simply syntactic sugar for a = a + b.

It is also not mutating. So a += b calculates a + b and then changes a to refer to the result. This means there is memory allocation for the result of a + b.