Luhn docs

luhn/luhn.go

@@ -1,14 +1,18 @@
+// Package luhn generates and validates Luhn mod N check digits.
 package luhn
 
 import "strings"
 
+// An alphabet is a string of N characters, representing the digits of a given
+// base N.
 type Alphabet string
 
 var (
-	Base32        Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567="
-	Base32Trimmed Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
+	Base32 Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
 )
 
+// Generate returns a check digit for the string s, which should be composed
+// of characters from the Alphabet a.
 func (a Alphabet) Generate(s string) rune {
 	factor := 1
 	sum := 0
@@ -30,6 +34,8 @@ func (a Alphabet) Generate(s string) rune {
 	return rune(a[checkCodepoint])
 }
 
+// Validate returns true if the last character of the string s is correct, for
+// a string s composed of characters in the alphabet a.
 func (a Alphabet) Validate(s string) bool {
 	t := s[:len(s)-1]
 	c := a.Generate(t)

luhn/luhn_test.go

@@ -7,11 +7,19 @@ import (
 )
 
 func TestGenerate(t *testing.T) {
+	// Base 6 Luhn
 	a := luhn.Alphabet("abcdef")
 	c := a.Generate("abcdef")
 	if c != 'e' {
 		t.Errorf("Incorrect check digit %c != e", c)
 	}
+
+	// Base 10 Luhn
+	a = luhn.Alphabet("0123456789")
+	c = a.Generate("7992739871")
+	if c != '3' {
+		t.Errorf("Incorrect check digit %c != 3", c)
+	}
 }
 
 func TestValidate(t *testing.T) {