Calculator without eval function

Do you all have without eval() function uses a calculator(with all brackets )?
I do not know how can I self-create an own eval() function.

I’m sure it’s a case of some do, some don’t.

A lot of people use eval for this challenge and there is really nothing wrong with using eval as long as you control the input to it. It’s maybe not optimal, but it’s not the end of the world either.

Not sure what you mean by creating your own eval?