我们应该如何计算货币（十进制，大浮点数）

Question

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

Answer 1

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
", 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
", c/10000, c%10000/100)
}

Playground: https://play.golang.org/p/YGW9SC7OcU3

Output:

1550
3100
4650
$0.47