ex03

ch11/ex03/go.mod

@@ -0,0 +1,3 @@
+module ch11/ex03
+
+go 1.15

ch11/ex03/random_word_test.go

@@ -0,0 +1,43 @@
+package word
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func randomPalindrome(rng *rand.Rand) string {
+	n := rng.Intn(25) // random length up to 24
+	runes := make([]rune, n)
+	for i := 0; i < (n+1)/2; i++ {
+		r := rune(rng.Intn(0x1000)) // random rune up to '\u0999'
+		runes[i] = r
+		runes[n-1-i] = r
+	}
+	return string(runes)
+}
+
+func randomNonPalindrome(rng *rand.Rand) string {
+	n := rng.Intn(23) + 3
+	runes := make([]rune, n)
+	for i := 0; i < (n+1)/2; i++ {
+		r1 := rune(65 + rng.Intn(13))
+		r2 := rune(78 + rng.Intn(13))
+		runes[i] = r1
+		runes[n-1-i] = r2
+	}
+	return string(runes)
+}
+
+func TestRandomPalindrome(t *testing.T) {
+	seed := time.Now().UTC().UnixNano()
+	t.Logf("Random seed: %d", seed)
+	rng := rand.New(rand.NewSource(seed))
+
+	for i := 0; i < 1000; i++ {
+		p := randomNonPalindrome(rng)
+		if IsPalindrome(p) {
+			t.Errorf("IsPalindrome(%q) = true", p)
+		}
+	}
+}

ch11/ex03/word.go

@@ -0,0 +1,20 @@
+package word
+
+import (
+	"unicode"
+)
+
+func IsPalindrome(s string) bool {
+	var letters []rune
+	for _, r := range s {
+		if unicode.IsLetter(r) {
+			letters = append(letters, unicode.ToLower(r))
+		}
+	}
+	for i := range letters {
+		if letters[i] != letters[len(letters)-1-i] {
+			return false
+		}
+	}
+	return true
+}