Go: Converting float64 to int with multiplier

Question

I want to convert a float64 number, let\'s say it 1.003 to 1003 (integer type). My implementation is simply multiply the float64

Answer 1

This is probably likely a problem with floating points in general in most programming languages though some have different implementations than others. I wouldn't go into the intricacies here but most languages usually have a "decimal" approach either as a standard library or a third party library to get finer precision.

For instance, I've found the inf.v0 package largely useful. Underlying the library is a Dec struct that holds the exponents and the integer value. Therefore, it's able to hold 1.003 as 1003 * 10^-3. See below for an example:

package main

import (
    "fmt"

    "gopkg.in/inf.v0"
)

func main() {
    // represents 1003 * 10^-3
    someDec := inf.NewDec(1003, 3)

    // multiply someDec by 1000 * 10^0
    // which translates to 1003 * 10^-3 * 1000 * 10^0
    someDec.Mul(someDec, inf.NewDec(1000, 0))

    // inf.RoundHalfUp rounds half up in the 0th scale, eg. 0.5 rounds to 1
    value, ok := someDec.Round(someDec, 0, inf.RoundHalfUp).Unscaled()
    fmt.Println(value, ok)
}

Hope this helps!