Error in the Auto-Optimizer code

[MatheusBazzo]

Hello everyone, I am having an error in writing the code attached below. Here is also a screenshot of the screen.

How could I correct the writing?

Thank you all.

[William Roeder]

You are defining a function. What does that return?

 ???   CAuto_optimizer::virtual_optimizer(void) {

[MatheusBazzo]

William Roeder #:

You are defining a function. What does that return?

Basically the whole code is an automatic optimizer for working with logistic regression.

It is a ready-made code I am studying, so I don't know exactly what this line returns and why this error.

I welcome suggestions on how to solve this.

Thank you.