Are there more elegant ways to prevent negative numbers in Ruby?

Question

Given that I\'d like to do the following calculation:

total = subtotal - discount

Because discount might be greater than

Answer 1

I think your solution is essentially correct, and probably the most readable besides a small refactor. I might change it slightly like so:

  def total
    final_total = subtotal - discount
    [final_total, 0].max
  end

The ruby expression [final_total, 0].max is essentially the traditional solution in mathematics for the same function: max {final_total, 0}. The difference is just notation and context. Once you see this max expression once or twice you can read it as follows: "final_total, but at least zero".

Perhaps if you use this expression more than once you can add another at_least_zero method or something like in Shiko's solution.