Add cmdline help & version info

2 files changed, 42 insertions, 14 deletions

diff --git a/args.go b/args.go
index 517cb21..10c28b1 100644
--- a/args.go
+++ b/args.go
@@ -2,37 +2,61 @@ package main
 
 import (
 	"errors"
-	"fmt"
 	"flag"
+	"fmt"
 	"strconv"
 )
 
+const ProgramVersion = "1.0.0-alpha+dev"
+
 // The arguments to this program
 type args struct {
-	Radix uint
+	Radix   uint
 	Compact bool
+	// If true, exit the program immediately after parsing args.
+	Exit bool
 }
 
 func parseArgs() (args, error) {
 	var a args
 	flag.BoolVar(&a.Compact, "c", false, "Compact the output display")
+	help := flag.Bool("?", false,
+		"Get information about program usage then exit")
+	version := flag.Bool("V", false,
+		"Print program version then exit")
 	flag.Parse()
 
-	if flag.NArg() == 1 {
-		if radix, err := strconv.ParseUint(flag.Arg(0), 0, 0); err == nil {
-			if radix > 1 {
-				a.Radix = uint(radix)
-				return a, nil
+	if *help {
+		printHelp()
+		return args{Exit: true}, nil
+	} else if *version {
+		fmt.Println("Radix Info version", ProgramVersion)
+		return args{Exit: true}, nil
+	} else {
+		if flag.NArg() == 1 {
+			if radix, err := strconv.ParseUint(flag.Arg(0), 0, 0); err == nil {
+				if radix > 1 {
+					a.Radix = uint(radix)
+					return a, nil
+				} else {
+					return args{}, errors.New("Radix must be an integer above 1.")
+				}
 			} else {
-				return args{}, errors.New("Radix must be an integer above 1.")
+				return args{}, fmt.Errorf(
+					"Argument must be an integer above 1 [%w].", err)
 			}
+		} else if flag.NArg() < 1 {
+			return args{}, errors.New("Please provide an argument (radix to study).")
 		} else {
-			return args{}, fmt.Errorf(
-				"Argument must be an integer above 1 [%w].", err)
+			return args{}, errors.New("Too many arguments provided.")
 		}
-	} else if flag.NArg() < 1 {
-		return args{}, errors.New("Please provide an argument (radix to study).")
-	} else {
-		return args{}, errors.New("Too many arguments provided.")
 	}
 }
+
+func printHelp() {
+	fmt.Println("Get important information about a radix.")
+	fmt.Println("You must provide one argument, which is the radix to get information about.")
+	fmt.Println("Usage: radix_info [flags...] <radix>")
+	fmt.Println("Options:")
+	flag.PrintDefaults()
+}
diff --git a/radix_info.go b/radix_info.go
index 04a8228..fb1caef 100644
--- a/radix_info.go
+++ b/radix_info.go
@@ -7,6 +7,10 @@ import (
 
 func main() {
 	args, err := parseArgs()
+	if args.Exit {
+		return
+	}
+
 	if err == nil {
 		factorInfo := GetFactorInfo(args.Radix)
 		if args.Compact {