Rounding Error with Decimal Sum

Afaik excel does use floats, so maybe it’s excel, which is wrong.

all my values are 2-decimal places
The Validator Program (some proprietor java program) also tells me the sum is wrong:

MMR100: Total is not equal to sum of all monthly balance for scheme…

When i manually adjust the sum to that excel value and feed it to the validator .. it validates

Parsing and summing the list as float gives: 208505442949.07806, rounding this to 2 decimal places returns 208505442949.08, so obviously Excel and your verification program do use floats and therefore are inaccurate by design…

PS: I’ve heard there are still people using Excel to manage their money…

PPS: my iex session:

iex(3)> File.read!("MMR100.txt") |> String.split() |> Enum.map(&String.to_float/1) |> Enum.sum
208505442949.07806
iex(4)> File.read!("MMR100.txt") |> String.split() |> Enum.map(&String.to_float/1) |> Enum.sum |> Float.round(2)
208505442949.08

All the numbers in that list are 2-dp, how can you get 208505442949.07806 ???

The magic of floats.

This exactly is the reason, why you’d even need a library like Decimal. Because floats are not suited for calculating correctly.

Every single finance department i have dealt with keeps parallel records in excel.

For some some reason there is an innate distrust of records from IT systems

No, I do get 9:

iex()> File.read!("MMR100.txt") |> String.split() |> Enum.map(&String.graphemes/1) |> Enum.map(&List.last/1) |> Enum.map(&String.to_integer/1) |> Enum.sum
1349409

Bah. I only looked at the text in the post. Did not notice the “this file has been truncated”…