Dev (#20)

* Dev

hashtable.go

@@ -397,3 +397,86 @@ func (hashtable *Hashtable[K, V]) HasMany(keys ...K) *slice.Slice[bool] {
 	}
 	return &values
 }
+
+// Keys returns a slice containing all the keys present in the hashtable.
+//
+// Example:
+//
+//	ht := make(hashtable.Hashtable[string, int])
+//	ht.Add("apple", 5)
+//	ht.Add("banana", 3)
+//	ht.Add("cherry", 8)
+//
+//	// Get all keys from the hashtable.
+//	keys := ht.Keys() // Result: {"apple", "banana", "cherry"}
+func (hashtable *Hashtable[K, V]) Keys() *slice.Slice[K] {
+	keys := make(slice.Slice[K], 0)
+	hashtable.EachKey(func(key K) {
+		keys.Append(key)
+	})
+	return &keys
+}
+
+// KeysFunc returns a slice containing the keys from the hashtable for which the provided function returns true.
+// The provided function `fn` should accept a key of type `K` and return a boolean value.
+//
+// Example:
+//
+//	ht := make(hashtable.Hashtable[string, int])
+//	ht.Add("apple", 5)
+//	ht.Add("banana", 3)
+//	ht.Add("cherry", 8)
+//
+//	// Get keys from the hashtable where the key length is greater than 5.
+//	keys := ht.KeysFunc(func(key string) bool {
+//	    return len(key) > 5
+//	})
+//	// Result: {"banana"}
+func (hashtable *Hashtable[K, V]) KeysFunc(fn func(key K) bool) *slice.Slice[K] {
+	keys := make(slice.Slice[K], 0)
+	hashtable.EachKey(func(key K) {
+		if fn(key) {
+			keys.Append(key)
+		}
+	})
+	return &keys
+}
+
+// Length returns the number of key-value pairs in the hashtable.
+//
+// Example:
+//
+//	ht := make(hashtable.Hashtable[string, int])
+//	ht.Add("apple", 5)
+//	ht.Add("banana", 3)
+//	ht.Add("cherry", 8)
+//
+//	length := ht.Length() // Result: 3
+func (hashtable *Hashtable[K, V]) Length() int {
+	return len(*hashtable)
+}
+
+// Map applies a given function to all key-value pairs in the hashtable and returns a new hashtable with the transformed values.
+// The original hashtable remains unchanged.
+//
+// Example:
+//
+//	ht := make(hashtable.Hashtable[string, int])
+//	ht.Add("apple", 5)
+//	ht.Add("banana", 3)
+//	ht.Add("cherry", 8)
+//
+//	// Define a function to double the values.
+//	doubleValue := func(key string, value int) int {
+//	    return value * 2
+//	}
+//
+//	// Apply the function to double the values in the hashtable.
+//	doubledHT := ht.Map(doubleValue)
+//	// doubledHT contains: {"apple": 10, "banana": 6, "cherry": 16}
+func (hashtable *Hashtable[K, V]) Map(fn func(key K, value V) V) *Hashtable[K, V] {
+	for key, value := range *hashtable {
+		hashtable.Add(key, fn(key, value))
+	}
+	return hashtable
+}

hashtable_test.go

@@ -3,6 +3,7 @@ package hashtable_test
 import (
 	"reflect"
 	"sort"
+	"strings"
 	"testing"
 
 	"github.com/lindsaygelle/hashtable"
@@ -424,11 +425,12 @@ func TestEachValueBreak(t *testing.T) {
 	ht.Add("banana", 3)
 	ht.Add("cherry", 8)
 
-	// Sort the keys for consistent iteration order.
 	keys := make([]string, 0, len(ht))
 	for key := range ht {
 		keys = append(keys, key)
 	}
+
+	// Sort the keys for consistent iteration order.
 	sort.Strings(keys)
 
 	// Define a function to process each value. It returns false to break the iteration if the value is 3.
@@ -529,9 +531,9 @@ func TestHas(t *testing.T) {
 func TestHasMany(t *testing.T) {
 	// Create a new hashtable.
 	ht := make(hashtable.Hashtable[string, int])
-	ht.Add("apple", 5)
-	ht.Add("banana", 3)
-	ht.Add("cherry", 8)
+	ht["apple"] = 5
+	ht["banana"] = 3
+	ht["cherry"] = 8
 
 	// Keys to check existence.
 	keysToCheck := []string{"apple", "orange", "banana"}
@@ -547,3 +549,71 @@ func TestHasMany(t *testing.T) {
 		t.Fatalf("Expected results: %v, but got: %v", expectedResults, results)
 	}
 }
+
+// TestKeys tests Hashtable.Keys.
+func TestKeys(t *testing.T) {
+	// Create a new hashtable.
+	ht := make(hashtable.Hashtable[string, int])
+	ht["apple"] = 5
+	ht["banana"] = 3
+	ht["cherry"] = 8
+
+	// Get all keys from the hashtable.
+	keys := ht.Keys()
+
+	// Sort the keys for consistent iteration order.
+	sort.Strings(*keys)
+
+	// The expected keys slice: {"apple", "banana", "cherry"}
+	expectedKeys := &slice.Slice[string]{"apple", "banana", "cherry"}
+
+	// Sort the keys for consistent iteration order.
+	sort.Strings(*expectedKeys)
+
+	// Verify that the obtained keys match the expected keys.
+	if !reflect.DeepEqual(keys, expectedKeys) {
+		t.Errorf("Expected keys: %v, but got: %v", expectedKeys, keys)
+	}
+}
+
+// TestKeysFunc tests Hashtable.KeysFunc.
+func TestKeysFunc(t *testing.T) {
+	// Create a new hashtable.
+	ht := make(hashtable.Hashtable[string, int])
+	ht["apple"] = 5
+	ht["banana"] = 3
+	ht["cherry"] = 8
+
+	// Get keys from the hashtable where the key length is greater than 5.
+	keys := ht.KeysFunc(func(key string) bool {
+		return strings.HasPrefix(key, "b")
+	})
+
+	// The expected keys slice: {"banana"}
+	expectedKeys := &slice.Slice[string]{"banana"}
+
+	// Verify that the obtained keys match the expected keys.
+	if !reflect.DeepEqual(keys, expectedKeys) {
+		t.Errorf("Expected keys: %v, but got: %v", expectedKeys, keys)
+	}
+}
+
+// TestLength tests Hashtable.Length.
+func TestLength(t *testing.T) {
+	// Create a new hashtable.
+	ht := make(hashtable.Hashtable[string, int])
+	ht["apple"] = 5
+	ht["banana"] = 3
+	ht["cherry"] = 8
+
+	// Get the length of the hashtable.
+	length := ht.Length()
+
+	// Expected length: 3
+	expectedLength := 3
+
+	// Verify that the obtained length matches the expected length.
+	if length != expectedLength {
+		t.Errorf("Expected length: %d, but got: %d", expectedLength, length)
+	}
+}