Reverse Polish Notation Calculator

main.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strconv"
	"strings"
)

func main() {
	// Read the Reverse Polish Expression from Stdin
	in, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		log.Fatal("Unable to read input")
	}

	equation := strings.Split(string(in), " ")
	results := []uint64{}

	for _, part := range equation {
		if n, err := strconv.ParseUint(part, 10, 32); err == nil {
			// Is numeric
			results = append(results, n)
		} else {
			// Is operator
			// Pick operands
			left := results[len(results)-2]
			right := results[len(results)-1]
			results = results[:len(results)-2]

			// Perform operation
			var out uint64
			switch part {
			case "+":
				out = left + right
				break
			case "-":
				out = left - right
				break
			case "*":
				out = left * right
				break
			case "/":
				out = left / right
				break
			}
			results = append(results, out)
		}
		log.Printf("WIP Results: %v\n", results)
	}

	if len(results) != 1 {
		log.Fatal("Error in computation")
	}

	fmt.Println(results[0])
}