decimal

Repository: shopspring/decimal: Arbitrary-precision fixed-point decimal numbers in go (github.com)

Documentation: decimal package - github.com/shopspring/decimal - Go Packages

Introduction

A decimal floating point utility library written in Go with the following features:

• Zero value is 0, safe to use without initialization
• Addition, subtraction, multiplication without loss of precision
• Division with specified precision
• Database/sql serialization/deserialization
• JSON and XML serialization/deserialization

Installation

go get github.com/shopspring/decimal

Quick Start

package main

import (
  "fmt"
  "github.com/shopspring/decimal"
)

func main() {
  price, err := decimal.NewFromString("136.02")
  if err != nil {
    panic(err)
  }

  quantity := decimal.NewFromInt(3)

  fee, _ := decimal.NewFromString(".035")
  taxRate, _ := decimal.NewFromString(".08875")

  subtotal := price.Mul(quantity)

  preTax := subtotal.Mul(fee.Add(decimal.NewFromFloat(1)))

  total := preTax.Mul(taxRate.Add(decimal.NewFromFloat(1)))

  fmt.Println("Subtotal:", subtotal)                      // Subtotal: 408.06
  fmt.Println("Pre-tax:", preTax)                         // Pre-tax: 422.3421
  fmt.Println("Taxes:", total.Sub(preTax))                // Taxes: 37.482861375
  fmt.Println("Total:", total)                            // Total: 459.824961375
  fmt.Println("Tax rate:", total.Sub(preTax).Div(preTax)) // Tax rate: 0.08875
}