Doing BigDecimal accounting with Ruby. When can I convert to float? - ruby

Question

I basically want to know the best to convert my BigDecimal numbers to readable format (float perhaps) for the purposes of displaying them to the client:
In order to figure out liabilities, I do contributions - distributions from each address.
For example, if a person contributes 2 units to an address and that same address distributes 1 unit back to the person, then there is still a 1 unit liability. that's what's going on below. These numbers are all units of cryptocurrency.
Here's another example:
Say address1 and address2 contribute 2 coins each to address3, and address3 distributes 1.0 coins to address1 and 0.5 coins to address2, then address3 has a 1.0 coin liability to address1 and a 1.5 coin liability to address2.
So the actual data using BigDecimal below:
contributions =
{"1444"=>#<BigDecimal:7f915c08f030,'0.502569E2',18(36)>,
"alice"=>#<BigDecimal:7f915c084018,'0.211E1',18(27)>,
"address1"=>#<BigDecimal:7f915c0a4430,'0.87161E1',18(36)>,
"address2"=>#<BigDecimal:7f915c0943f0,'0.84811E1',18(36)>,
"address3"=>#<BigDecimal:7f915c0a43e0,'0.385E0',9(18)>,
"address6"=>#<BigDecimal:7f915c09ebe8,'0.1E1',9(18)>,
"address7"=>#<BigDecimal:7f915c09eb98,'0.1E1',9(18)>,
"address8"=>#<BigDecimal:7f915c09d428,'0.15E1',18(18)>,
"address9"=>#<BigDecimal:7f915c09d3d8,'0.15E1',18(18)>,
"address10"=>#<BigDecimal:7f915c0a7540,'0.132E1',18(36)>,
"address11"=>#<BigDecimal:7f915c0af8a8,'0.392E1',18(36)>,
"address12"=>#<BigDecimal:7f915c0a4980,'0.14E1',18(36)>,
"address13"=>#<BigDecimal:7f915c0af858,'0.2133333333 3333333333 33333334E1',36(54)>,
"address14"=>#<BigDecimal:7f915c0a54c0,'0.3533333333 3333333333 33333334E1',36(45)>,
"address15"=>#<BigDecimal:7f915c0a66e0,'0.1533333333 3333333333 33333334E1',36(36)>,
"sdfds"=>#<BigDecimal:7f915c0a6118,'0.1E0',9(27)>,
"sf"=>#<BigDecimal:7f915c0a6028,'0.1E0',9(27)>,
"address20"=>#<BigDecimal:7f915c0ae688,'0.3E0',9(18)>,
"address21"=>#<BigDecimal:7f915c0ae638,'0.3E0',9(18)>,
"address23"=>#<BigDecimal:7f915c0ae070,'0.1E0',9(27)>,
"address22"=>#<BigDecimal:7f915c0adf80,'0.1E0',9(27)>,
"add1"=>#<BigDecimal:7f915c0ad328,'0.1E0',9(18)>,
"add2"=>#<BigDecimal:7f915c0ad2d8,'0.1E0',9(18)>,
"addx"=>#<BigDecimal:7f915c0acd10,'0.1E0',9(27)>,
"addy"=>#<BigDecimal:7f915c0acc20,'0.1E0',9(27)>}
and the distributions:
distributions =
{"1444"=>#<BigDecimal:7f915a9068f0,'0.502569E2',18(63)>,
"alice"=>#<BigDecimal:7f915a8f44e8,'0.211E1',18(27)>,
"address1"=>#<BigDecimal:7f915a906800,'0.87161E1',18(54)>,
"address2"=>#<BigDecimal:7f915a906710,'0.84811E1',18(54)>,
"address3"=>#<BigDecimal:7f915a906620,'0.385E0',9(36)>,
"address6"=>#<BigDecimal:7f915a8fdea8,'0.1E1',9(27)>,
"address7"=>#<BigDecimal:7f915a8fddb8,'0.1E1',9(27)>,
"address8"=>#<BigDecimal:7f915a8fd5e8,'0.15E1',18(18)>,
"address9"=>#<BigDecimal:7f915a8fd4f8,'0.15E1',18(18)>,
"address10"=>#<BigDecimal:7f915a8fc9b8,'0.132E1',18(36)>,
"address11"=>#<BigDecimal:7f915a9071b0,'0.3920000000 0000003E1',27(45)>,
"address12"=>#<BigDecimal:7f915a907660,'0.1400000000 0000001E1',27(36)>,
"address13"=>#<BigDecimal:7f915a9070c0,'0.2133333333 3333337E1',27(45)>,
"address14"=>#<BigDecimal:7f915a906530,'0.3533333333 3333333333 33333334E1',36(54)>,
"address15"=>#<BigDecimal:7f915a8fc148,'0.1533333333 3333334E1',27(27)>,
"sdfds"=>#<BigDecimal:7f915a907f98,'0.1E0',9(27)>,
"sf"=>#<BigDecimal:7f915a907e08,'0.1E0',9(27)>,
"address20"=>#<BigDecimal:7f915a906ad0,'0.3000000000 0000003E0',18(27)>,
"address21"=>#<BigDecimal:7f915a9069e0,'0.3000000000 0000003E0',18(27)>,
"address23"=>#<BigDecimal:7f915a9063c8,'0.1E0',9(27)>,
"address22"=>#<BigDecimal:7f915a906238,'0.1E0',9(27)>,
"add1"=>#<BigDecimal:7f915a9060a8,'0.5E-1',9(27)>,
"add2"=>#<BigDecimal:7f915a905f18,'0.1E0',9(27)>}
Ideally, I want my liabilities to look like this:
{"add1"=>0.05,
"addx"=>0.1>,
"addy"=>0.1>}
But they look like this:
{"1444"=>0.0,
"alice"=>0.0,
"address1"=>0.0,
"address2"=>0.0,
"address3"=>0.0,
"address6"=>0.0,
"address7"=>0.0,
"address8"=>0.0,
"address9"=>0.0,
"address10"=>0.0,
"address11"=>-3.0e-16,
"address12"=>-1.0e-16,
"address13"=>-3.66666666666e-16,
"address14"=>0.0,
"address15"=>-6.6666666666e-17,
"sdfds"=>0.0,
"sf"=>0.0,
"address20"=>-3.0e-17,
"address21"=>-3.0e-17,
"address23"=>0.0,
"address22"=>0.0,
"add1"=>0.05,
"add2"=>0.0,
"addx"=>#<BigDecimal:7f915c0acd10,'0.1E0',9(27)>,
"addy"=>#<BigDecimal:7f915c0acc20,'0.1E0',9(27)>}
I don't want to include -3.66666666666e-16 because that's essentially 0 and even Ruby accounts for it this way when you run -3.66666666666e-16 > 0... it returns false.
This is what I have... is the a better way? The code below is calculating the liabilities by subtracting con from dis and only selecting the liabilities that are greater than 0.0...that makes sense to me and it excludes 1-time grants of coins (there must be a matching contribution to be a liability). Then, I convert everything to floats so it's readable. Does this look right?
liab = #contributions.merge(#distributions) do |key, con, dis|
(con - dis)
end.select { |addr, amount| amount > 0.0 && #contributions.keys.include?(addr) }
liab.merge(liab) do |k, old, new|
k = new.to_f
end
I want the amount returned in float format, not the big decimal object. Is what I'm doing okay? Will I keep accuracy if I convert to float at the end?