FWIW, in some code I am writing, I considered using
fixed point decimal numbers but ended up defining a
*currency* type which is an int64 for value + a separate
unit + currency kind. Even if I use a unit of millicent, this
will allow handling amounts close to $100 Trillion. I
don't expect this limit to be a problem for my personal
finances! Performance is not an issue for my use. I
even store all the financial data in text files!
Dealing with stuff such as currency conversion, interest
rates, stocks etc. gets a bit complicated due to their own
precision needs but for that one can look at existing
practices to do the right thing (which is, be able to accurately
implement the rules your bank etc use).
[Aside:
Ideally this would be done using a *generic* currency
type. Something like
import "currency"
type $ = currency.Type("$")
type £ = currency.Type("£")
var m1 = $(5)
var m2 = $(10)
var m3 = £(2)
m1 + m2 // ok
m2 + m3 // compile time error
m1*m2 // compile time error
m1*5 // ok
m1+5 // compile time error
I doubt go2 will get generics flexible enough for this!
]
> On Nov 28, 2018, at 10:47 PM, robert engels <reng...@ix.netcom.com> wrote:
>
> For those interesting in financial apps, I have released ‘fixed' at
> https://github.com/robaho/fixed <https://github.com/robaho/fixed> a high
> performance fixed-point math library primarily designed for to work with
> currencies.
>
> The benchmarks: (Decimal is the shopspring library, big Int/Float are the
> stdlib)
>
> BenchmarkAddFixed-8 2000000000 0.83 ns/op
> 0 B/op 0 allocs/op
> BenchmarkAddDecimal-8 3000000 457 ns/op
> 400 B/op 10 allocs/op
> BenchmarkAddBigInt-8 100000000 19.2 ns/op
> 0 B/op 0 allocs/op
> BenchmarkAddBigFloat-8 20000000 110 ns/op
> 48 B/op 1 allocs/op
> BenchmarkMulFixed-8 100000000 12.4 ns/op
> 0 B/op 0 allocs/op
> BenchmarkMulDecimal-8 20000000 94.2 ns/op
> 80 B/op 2 allocs/op
> BenchmarkMulBigInt-8 100000000 22.0 ns/op
> 0 B/op 0 allocs/op
> BenchmarkMulBigFloat-8 30000000 50.0 ns/op
> 0 B/op 0 allocs/op
> BenchmarkDivFixed-8 100000000 19.3 ns/op
> 0 B/op 0 allocs/op
> BenchmarkDivDecimal-8 1000000 1152 ns/op
> 928 B/op 22 allocs/op
> BenchmarkDivBigInt-8 20000000 68.4 ns/op
> 48 B/op 1 allocs/op
> BenchmarkDivBigFloat-8 10000000 151 ns/op
> 64 B/op 2 allocs/op
> BenchmarkCmpFixed-8 2000000000 0.28 ns/op
> 0 B/op 0 allocs/op
> BenchmarkCmpDecimal-8 100000000 10.8 ns/op
> 0 B/op 0 allocs/op
> BenchmarkCmpBigInt-8 200000000 8.37 ns/op
> 0 B/op 0 allocs/op
> BenchmarkCmpBigFloat-8 200000000 7.74 ns/op
> 0 B/op 0 allocs/op
> BenchmarkStringFixed-8 20000000 99.0 ns/op
> 16 B/op 1 allocs/op
> BenchmarkStringDecimal-8 5000000 326 ns/op
> 144 B/op 5 allocs/op
> BenchmarkStringBigInt-8 10000000 209 ns/op
> 80 B/op 3 allocs/op
> BenchmarkStringBigFloat-8 3000000 571 ns/op
> 272 B/op 8 allocs/op
>
>
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