Example (Go) - Investment Calculator

module example.com/investment-calculator

go 1.21.6

package main

import (
	"fmt"
	"math"
)

const inflationRate float64 = 2.5

func main() {
	//! ====Go can automatically infer the type.====
	// investmentAmount := 1000

	//! ====It is also possible to declare a type.====
	// var investmentAmount float64 = 1000

	//! ====Instatiate the variable and can edit it later====
	var investmentAmount float64

	//! ====It is possible to declare multiple variables in one go====
	// var investmentAmount, years float64 = 1000, 10
	// investmentAmount, years := 1000.0, 10.0
	// investmentAmount, years, expectedReturnRate := 1000.0, 10.0, 5.5

	//! ====In some cases it is also possible to define variables of different types====
	// var investmentAmount, years = 1000, "10"

	var expectedReturnRate float64 = 5.5

	// float64 := 10
	var years float64 = 10

	//! ====Constants can be declared with const keyword====
	// const inflationRate float64 = 2.5

	fmt.Print("Investment Amount: ")
	//! ====Need to pass pointers for fmt.Scan====
	fmt.Scan(&investmentAmount)

	// fmt.Print("Expected Return Rate: ")
	outputText("Expected Return Rate: ")
	fmt.Scan(&expectedReturnRate)

	fmt.Print("Investment Horizon: ")
	fmt.Scan(&years)

	// ====Can convert variables between data types with a wrap float64() or int()====
	// futureValue := float64(investmentAmount) * math.Pow(1+expectedReturnRate/100, float64(years))
	// var futureValue float64 = investmentAmount * math.Pow(1+expectedReturnRate/100, years)
	// var futureRealValue float64 = futureValue / math.Pow(1+inflationRate/100, years)

	//! ====Use function to calculate future values instead====
	futureValue, futureRealValue := calculateFutureValues(investmentAmount, expectedReturnRate, years)

	// ====Different ways to print statements====
	// fmt.Println("Future value before inflation:", futureValue)
	// fmt.Println("Future value after inflation:", futureRealValue)
	// fmt.Printf("Future Value: %v\nFuture Value after Inflation: %v\n", futureValue, futureRealValue)
	// fmt.Printf("Future Value: %.0f\nFuture Value after Inflation: %.1f\n", futureValue, futureRealValue) //0.xf (where x is d.p.)

	formattedFV := fmt.Sprintf("Future Value: %.0f\n", futureValue)
	formattedRFV := fmt.Sprintf("Future Value after Inflation: %.1f\n", futureRealValue)
	fmt.Print(formattedFV, formattedRFV)
	// fmt.Printf(`Future Value: %.0f
	// Future Value after Inflation: %.1f`, futureValue, futureRealValue)
}

func outputText(text string) {
	fmt.Print(text)
}

// func calculateFutureValues(investmentAmount float64, expectedReturnRate float64, years float64) (float64, float64) {
// 	fv := investmentAmount * math.Pow(1+expectedReturnRate/100, years)
// 	rfv := fv / math.Pow(1+inflationRate/100, years)
// 	return fv, rfv
// }

// ====Another way to define functions with outputs====
func calculateFutureValues(investmentAmount float64, expectedReturnRate float64, years float64) (fv float64, rfv float64) {
	fv = investmentAmount * math.Pow(1+expectedReturnRate/100, years)
	rfv = fv / math.Pow(1+inflationRate/100, years)
	return
}