cli/cli.go

@@ -64,7 +64,7 @@ func (this *Cli) Parse (args []string) error {
 			err   := flag.Validate(value)
 			if err != nil {
 				return errors.New(fmt.Sprint (
-					"could not parse ", flag.String(), ": ",
+					"bad value for ", flag.String(), ": ",
 					err))
 			}
 			flag.Value = value
@@ -238,3 +238,19 @@ func ValInt (value string) error {
 	_, err := strconv.Atoi(value)
 	return err
 }
+
+// NewValSet returns a validation function that accepts a set of strings.
+func NewValSet (allowed ...string) func (value string) error {
+	return func (value string) error {
+		allowedFmt := ""
+		for index, test := range allowed {
+			if test == value { return nil }
+
+			if index > 0 { allowedFmt += ", " }
+			allowedFmt += test
+		}
+		return errors.New (
+			"value must be one of (" + allowedFmt + ")")
+	}
+}
+

cmd/fsplc/main.go

@@ -2,7 +2,6 @@ package main
 
 import "os"
 import "fmt"
-import "errors"
 import "git.tebibyte.media/sashakoshka/fspl/cli"
 import ferrors "git.tebibyte.media/sashakoshka/fspl/errors"
 
@@ -17,12 +16,7 @@ func main () {
 	optimization := cli.NewInputFlag (
 		'O', "optimization",
 		"Optimization level (0-3)", "0",
-	func (value string) error {
-		switch value {
-		case "0", "1", "2", "3": return nil
-		default: return errors.New("optimization level must be 0-3")
-		}
-	})
+		cli.NewValSet("0", "1", "2", "3"))
 
 	application := cli.New("Compile FSPL source files", help, output, optimization)
 	application.Syntax = "[OPTION]... [FILE]..."