Can someone tell the right way to calculate finance data in Go. I tryed to use big.Float but prob I miss something. The core goal is to calculate numbers with flaoting point and precision from 2 to 4 without any losses. 0.15 + 0.15
always should be 0.30. float
try: https://play.golang.org/p/_3CXtRRNcA0 big.Float
try: https://play.golang.org/p/zegE__Dit1O
Floating-point is imprecise. Use integers ( int64
) scaled to cents or fractional cents.
For example, cents,
package main
import (
"fmt"
)
func main() {
cents := int64(0)
for i := 0; i <= 2; i++ {
cents += 15
fmt.Println(cents)
}
fmt.Printf("$%d.%02d\n", cents/100, cents%100)
}
Playground: https://play.golang.org/p/k4mJZFRUGVH
Output:
15
30
45
$0.45
For example, hundredths of a cent rounded,
package main
import "fmt"
func main() {
c := int64(0) // hundredths of a cent
for i := 0; i <= 2; i++ {
c += 1550
fmt.Println(c)
}
c += 50 // rounded
fmt.Printf("$%d.%02d\n", c/10000, c%10000/100)
}
Playground: https://play.golang.org/p/YGW9SC7OcU3
Output:
1550
3100
4650
$0.47
you can try https://github.com/shopspring/decimal if you really concern about precision,
try this code:
package main
import (
"fmt"
"github.com/shopspring/decimal"
)
func main() {
z := decimal.NewFromFloat(0)
b := decimal.NewFromFloat(0.15)
z = z.Add(b)
z = z.Add(b)
z = z.Add(b)
fmt.Println("z value:", z)
testz := z.Cmp(decimal.NewFromFloat(0.45)) == 0
fmt.Println("is z pass the test? ", testz)
}
Playground: https://play.golang.org/p/g_fSGlXPKDH
Output:
z value: 0.45
is z pass the test? true
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