I am trying to make a simple addition program, but when I put my let function in the viewDidLoad, it gives me this error:

> 
> initialization of immutable value 'doMath' was never used; consider
>  replacing with assignment to '\_' or removing it.
> 
> 
> 

Here is the code

```
let doMath: (Int!, Int!) -> Int =
mathFunction(text1, text2)
}

```

What should I do?