prices = ["1.6", "0.15", "1.8"]
prices.sum { |price| price.to_f }
But this returns 3.5500000000000003, not 3.55.
Any idea?
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Remy Wang
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Floating-point numbers cannot precisely represent all real numbers, and floating-point operations cannot precisely represent true arithmetic operations, this leads to many surprising situations.
I advise reading: https://en.wikipedia.org/wiki/Floating_point#Accuracy_problems
You may want to use BigDecimal to avoid such problems:
require 'bigdecimal'
prices = ["1.6", "0.15", "1.8"]
prices.sum { |price| BigDecimal(price) }
#=> 3.55
spickermann
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BigDecimal(nil) throws error. – Remy Wang Feb 24 '20 at 11:14
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1Of course. Where is the `nil` coming from? In the array in your original question there is no `nil`. – spickermann Feb 24 '20 at 11:37
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`["1.6", "0.15", "1.8", nil].sum(&:to_r).to_f` seems to work with nil. – steenslag Feb 24 '20 at 12:40
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1You can `require 'bigdecimal/util'` and use `["1.6", "0.15", "1.8", nil].sum(&:to_d)` instead which treats `nil` values as `0.0`, just like `to_f`. – Stefan Feb 24 '20 at 15:06