Have you ever had any bugs because of floats before?
I just had my first one and I hope I don’t get many of them.
Setup
Originally and proudly I help make a feature to sort and display points. The bars which displayed the points
also had to be relative in size to each other.
I will not show everything but I will show where the problem was.
Problem
I tested the expected behavior and the edge cases but I did not check for float errors.
If you want to know why floats can be inaccurate Here is a link!
My mistake was forgetting there could be errors there and also adding an unecessary ".00" before the percent sign.
Both of these caused certain particular values to become "41.9999999135.00%" instead of "42.00%"
(defn make-percentage [decimal]
(str (* 100 decimal)".00%"))
(defn calculate-percentages [total-points max-points]
(let [ratio (coerce-float (/ total-points max-points) 2)]
(make-percentage (max default-decimal ratio))))
Now I know what you are thinking. Why did you add this value ".00"? Well, it was because certain parts relied on
representing values that way. So I decided to make sure that was no longer the case.
Solution
Now I had to make sure again that the flot values would be rounded off correctly, and that I did not add the ".00" value manually.
(defn make-percentage [decimal]
(str (float->string (* 100 decimal) 2) "%"))
Now I can lay my head to rest knowing, there are no more bugs in my code.
I hope.
Best,
Merl