Why does this math look like this?

[gilded kayak]

Hi guys. Im learning go, and i just did something that i can't get. Could someone tell me why this float math returns some number like "860.9000000000001" ?

package main

import "fmt"

type CheckingAccount struct {
    owner        string
    agenceNumber int
    account      int
    ballance     float64
}

func (sender *CheckingAccount) Transfer(recipient *CheckingAccount, transferValue float64) bool {
    if transferValue > sender.ballance || transferValue <= 0 {
        return false
    }

    sender.ballance -= transferValue
    recipient.ballance += transferValue
    return true
}

func main() {
    account := CheckingAccount{
        owner:        "Antonio",
        agenceNumber: 0567,
        account:      123456,
        ballance:     1380.90,
    }

    account2 := CheckingAccount{
        "Antonio",
        0567,
        123456,
        1380.90,
    }

    fmt.Println(account, account2)
    account.Transfer(&account2, 520.)
    fmt.Println(account, account2)
}

output:

{Antonio 375 123456 1380.9} {Antonio 375 123456 1380.9}
{Antonio 375 123456 860.9000000000001} {Antonio 375 123456 1900.9}

[orchid geyser]

https://www.youtube.com/watch?v=Oo89kOv9pVk explains it in way too much detail

slightly above absolutely no one uses floats for monetary computations, fixed point math is what is used

so you use uint or int but with a scalling factor

[rustic radish]

That's an inherant property of floating point numbers.

Never use floats when you want accuracy.

[gilded kayak]

did not know about that

appreciated guys !

[verbal obsidian]

Yeah I don’t know why a lot of coding examples use floats for money it’s a really bad idea