readysteady/percentage

Ruby gem for working with percentages

percentage's Issues

Error on `change` method ZeroDivisionError: divided by 0

I am using this gem to calculate the percentage but getting error sometimes when the min value is o, for example

percentage = Percentage.change(0, 1)

in that case I am getting error like

ZeroDivisionError: divided by 0
from /usr/local/bundle/gems/percentage-1.4.1/lib/percentage.rb:118:in `/'

if you can manage it in some good manner so that can be easy to handle from the developers end.

Thoughts on Class variable for default truncation

Adding .truncate(2) after every call to Percentage.new when displaying the information in a table is rather tedious.

What are your thoughts on having an option to set truncation for future calls?
Something like the following would be nice and easy to implement.

Percentage.default_truncation = 2
Percentage.new(Rational(1,3)).to_s
# => 0.33%

When working with rails you could then create an initialiser app/config/initializers/percentage.rb to set this globally.

# app/config/initializers/percentage.rb
Percentage.default_truncation = 2

Should Percentage be Numeric?

Thank you for the helpful library! I was recently investigating using it in place of our own internal implementation.

One issue that I ran into is that Percentage instances can't be used directly in arithmetic with Ruby Money, because they implement type checking. It took me a couple tries to get the behavior I wanted:

Money.new(10) * Percentage.new(10) # expecting => #<Money 1>
=> TypeError: Can't multiply a Money by a Percentage's value

then

Money.new(10) * Percentage.new(10).to_f # expecting => #<Money 1>
=> #<Money 100>

finally

Money.new(10) * Percentage.new(10).to_r
=> #<Money 1>

So I suppose I have a couple questions:

1. Have you considered making Percentage a subclass of Numeric since it does represent a numeric value? I believe you already have the required interfaces implemented (arithmetic and coerce).
2. I was surprised that the floating point conversion of a Percentage is not the percentage in decimal form. Why is that the case?

Thank you again for taking the time to read this, and thank you for maintaining a useful library ❤️💙💚💛💜

The multiplication and divisions operations seams wrong

See : https://towardsdatascience.com/most-people-screw-up-multiple-percent-changes-heres-how-to-do-get-them-right-b86bd6ef4b72

BigDecimal#percent_of

I'd like to be able to use decimals this way. However, I note that the library treats a decimal value between 0 and 1 as a percentage of 1. I'd prefer to keep it as a scale of 0 to 100. When I say "0.5 percent of 88", I don't mean 50 percent.

What do you think