Awesome

money

Package money implements immutable monetary amounts and exchange rates for Go.

Features

• Optimized Performance - Utilizes uint64 for coefficients, reducing heap allocations and memory consumption.
• High Precision - Supports 19 digits of precision, which allows representation of amounts between -99,999,999,999,999,999.99 and 99,999,999,999,999,999.99 inclusive.
• Immutability - Once an amount or exchange rate is set, it remains unchanged. This immutability ensures safe concurrent access across goroutines.
• Banker's Rounding - Methods use half-to-even rounding, also known as "banker's rounding", which minimizes cumulative rounding errors commonly seen in financial calculations.
• No Panics - All methods are designed to be panic-free. Instead of potentially crashing your application, they return errors for issues such as overflow, division by zero, or currency mismatch.
• Correctness - Fuzz testing is used to cross-validate arithmetic operations against the cockroachdb and shopspring decimal packages.

Getting started

Installation

To add the money package to your Go workspace:

go get github.com/govalues/money

Usage

Create amount using one of the constructors. After creating a monetary amount, various operations can be performed:

package main

import (
    "fmt"
    "github.com/govalues/decimal"
    "github.com/govalues/money"
)

func main() {
    // Constructors
    a, _ := money.NewAmount("USD", 8, 0)               // a = USD 8.00
    b, _ := money.ParseAmount("USD", "12.5")           // b = USD 12.50
    c, _ := money.NewAmountFromFloat64("USD", 2.567)   // c = USD 2.567
    d, _ := money.NewAmountFromInt64("USD", 7, 896, 3) // d = USD 7.896
    r, _ := money.NewExchRate("USD", "EUR", 9, 1)      // r = USD/EUR 0.9
    x, _ := decimal.New(2, 0)                          // x = 2

    // Operations
    fmt.Println(a.Add(b))          // USD 8.00 + USD 12.50
    fmt.Println(a.Sub(b))          // USD 8.00 - USD 12.50

    fmt.Println(a.Mul(x))          // USD 8.00 * 2
    fmt.Println(a.FMA(x, b))       // USD 8.00 * 2 + USD 12.50
    fmt.Println(r.Conv(a))         // USD 8.00 * USD/EUR 0.9

    fmt.Println(a.Quo(x))          // USD 8.00 / 2
    fmt.Println(a.QuoRem(x))       // USD 8.00 div 2, USD 8.00 mod 2
    fmt.Println(a.Rat(b))          // USD 8.00 / USD 12.50
    fmt.Println(a.Split(3))        // USD 8.00 into 3 parts

    // Rounding to 2 decimal places
    fmt.Println(c.RoundToCurr())   // 2.57
    fmt.Println(c.CeilToCurr())    // 2.57
    fmt.Println(c.FloorToCurr())   // 2.56
    fmt.Println(c.TruncToCurr())   // 2.56

    // Conversions
    fmt.Println(d.Int64(9))        // 7 896000000
    fmt.Println(d.Float64())       // 7.896
    fmt.Println(d.String())        // USD 7.896

    // Formatting
    fmt.Printf("%v\n", d)          // USD 7.896
    fmt.Printf("%[1]f %[1]c\n", d) // 7.896 USD
    fmt.Printf("%f\n", d)          // 7.896
    fmt.Printf("%c\n", d)          // USD
    fmt.Printf("%d\n", d)          // 790
}

Documentation

For detailed documentation and additional examples, visit the package documentation.

Comparison

Comparison with other popular packages:

Benchmarks

goos: linux
goarch: amd64
pkg: github.com/govalues/money-tests
cpu: AMD Ryzen 7 3700C  with Radeon Vega Mobile Gfx 

The benchmark results shown in the table are provided for informational purposes only and may vary depending on your specific use case.

Contributing

Interested in contributing? Here's how to get started:

1. Fork and clone the repository.
2. Implement your changes.
3. Write tests to cover your changes.
4. Ensure all tests pass with go test.
5. Commit and push to your fork.
6. Open a pull request detailing your changes.

Note: If you're considering significant changes, please open an issue first to discuss with the maintainers. This ensures alignment with the project's objectives and roadmap.