diff --git a/README.md b/README.md
index 482397c..bbbcaf2 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
 # collections-go
 
-A dependency-free package of generic Go collection data structures. Compatible with Go 1.18 and above.
+A dependency-free package of generic Go collection data structures. Compatible with Go 1.18 and above. Strives for the most optimal solutions available with lowest number of allocations.
+
+Contributions are not currently open as this project is in active early development.
diff --git a/predicate.go b/predicate.go
new file mode 100644
index 0000000..0fdf162
--- /dev/null
+++ b/predicate.go
@@ -0,0 +1,9 @@
+package collections
+
+// A UnaryPredicate is a function that takes a single element of type
+// T and returns a boolean.
+type UnaryPredicate[T any] func(T) bool
+
+// A UnaryOperator is a function that takes a single element of type
+// T and returns an element of type T.
+type UnaryOperator[T any] func(T) T
diff --git a/set.go b/set.go
index 72bdc1f..2fa21ff 100644
--- a/set.go
+++ b/set.go
@@ -6,16 +6,16 @@ package collections
 // empty struct initialization any time you add to the set.
 type Set[T comparable] map[T]struct{}
 
-// Initialize a new Set by providing a slice. The Set will have the
-// same type as the slice.
+// Initialize a new Set with a set of arguments. Good for if you want to initialize
+// a new set in place with values.
 //
-//	Time Complexity: O(n)
-//	Space Complexity: O(n)
-//	Allocations: 1 set, n elements
-func NewSet[T comparable](slice []T) Set[T] {
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+// Allocations: 1 set, n elements.
+func NewSet[T comparable](elements ...T) Set[T] {
 	set := make(Set[T])
-	for _, el := range slice {
-		set[el] = struct{}{}
+	for i := 0; i < len(elements); i++ {
+		set.Add(elements[i])
 	}
 	return set
 }
@@ -23,11 +23,11 @@ func NewSet[T comparable](slice []T) Set[T] {
 // Initialize a new set while preserving the elements that were found to be duplicate.
 // The duplicate slice will be nil if there are no duplicates to save on allocations.
 //
-//	Time Complexity: O(n)
-//	Space Complexity: O(n)
-//	Allocations (best case): 1 set, n elements
-//	Allocations (worst case): 1 set, n/2 elements, 2 slices, one with n-1 space, the
-//	other is the first one resized based on number of duplicates.
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+// Allocations (best case): 1 set, n elements
+// Allocations (worst case): 1 set, n/2 elements, 2 slices, one with n-1 space, the
+// second is the first one resized if necessary.
 func NewSetSaveDuplicates[T comparable](slice []T) (Set[T], []T) {
 	set := make(Set[T])
 	var dupes []T = nil
@@ -46,14 +46,17 @@ func NewSetSaveDuplicates[T comparable](slice []T) (Set[T], []T) {
 			set[el] = struct{}{}
 		}
 	}
-	return set, dupes[:dupesIdx]
+	if dupes != nil && dupesIdx < len(dupes)-1 {
+		dupes = dupes[:dupesIdx]
+	}
+	return set, dupes
 }
 
 // ToSlice will take all of the elements of the set and create a new slice out of them.
 //
-//	Time Complexity: O(n)
-//	Space Complexity: O(n)
-//	Allocations: 1 slice, n elements
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+// Allocations: 1 slice, n elements
 func (set Set[T]) ToSlice() []T {
 	slice := make([]T, len(set))
 	i := 0
@@ -66,27 +69,27 @@ func (set Set[T]) ToSlice() []T {
 
 // Add an element to the set.
 //
-//	Time Complexity: O(1)
-//	Space Complexity: O(1)
-//	Allocations: 1 elements
+// Time Complexity: O(1)
+// Space Complexity: O(1)
+// Allocations: 1 elements
 func (s Set[T]) Add(el T) {
 	s[el] = struct{}{}
 }
 
 // Remove an element from the set.
 //
-//	Time Complexity: O(1)
-//	Space Complexity: O(1)
-//	Allocations: None
+// Time Complexity: O(1)
+// Space Complexity: O(1)
+// Allocations: None
 func (s Set[T]) Remove(el T) {
 	delete(s, el)
 }
 
 // Check if the set contains a particular value.
 //
-//	Time Complexity: O(1)
-//	Space Complexity: O(1)
-//	Allocations: None
+// Time Complexity: O(1)
+// Space Complexity: O(1)
+// Allocations: None
 func (s Set[T]) Contains(el T) bool {
 	_, containsEl := s[el]
 	return containsEl
@@ -94,9 +97,9 @@ func (s Set[T]) Contains(el T) bool {
 
 // Creates a Clone of the set which contains all the same values.
 //
-//	Time Complexity: O(n)
-//	Space Complexity: O(n)
-//	Allocations: 1 set, n elements
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+// Allocations: 1 set, n elements
 func (s Set[T]) Clone() Set[T] {
 	clone := make(Set[T])
 	for el := range s {
@@ -107,9 +110,9 @@ func (s Set[T]) Clone() Set[T] {
 
 // Checks if the set is equal to another.
 //
-//	Time Complexity: O(n)
-//	Space Complexity: O(1)
-//	Allocations: None
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+// Allocations: None
 func (s Set[T]) Equals(s2 Set[T]) bool {
 	if len(s) != len(s2) {
 		return false
diff --git a/set_test.go b/set_test.go
index 08e0acd..aa6cff6 100644
--- a/set_test.go
+++ b/set_test.go
@@ -7,14 +7,14 @@ import (
 	"github.com/RageCage64/go-assert"
 )
 
-func TestSetToSlice(t *testing.T) {
-	set := collections.Set[int]{
-		1: {},
-		2: {},
-		3: {},
-	}
-	slice := set.ToSlice()
-	assert.SliceEqual(t, []int{1, 2, 3}, slice)
+func runNewSetTestCase[T comparable](t *testing.T, elements ...T) {
+	t.Helper()
+
+	compareSetAndSlice(t, collections.NewSet(elements...), elements)
+}
+
+func TestNewSet(t *testing.T) {
+	runNewSetTestCase(t, []int{1, 2, 3}...)
 }
 
 func runNewSetSaveDuplicatesTestCase[T comparable](
@@ -24,6 +24,7 @@ func runNewSetSaveDuplicatesTestCase[T comparable](
 	expectedDupes []T,
 ) {
 	t.Helper()
+
 	newSet, dupes := collections.NewSetSaveDuplicates(slice)
 	assert.Assert(
 		t,
@@ -76,3 +77,41 @@ func TestNewSetSaveDuplicates(t *testing.T) {
 		)
 	})
 }
+
+func runSetToSliceTestCase[T comparable](t *testing.T, set collections.Set[T], expected []T) {
+	assert.SliceEqual(t, expected, set.ToSlice())
+}
+
+func TestSetToSlice(t *testing.T) {
+	runSetToSliceTestCase(
+		t,
+		collections.Set[int]{
+			1: {},
+			2: {},
+			3: {},
+		},
+		[]int{1, 2, 3},
+	)
+}
+
+func compareSetAndSlice[T comparable](t *testing.T, set collections.Set[T], slice []T) {
+	t.Helper()
+
+	for _, el := range slice {
+		if !set.Contains(el) {
+			t.Fatalf("expected set to contain %v", el)
+		}
+	}
+	for el := range set {
+		found := false
+		for _, sliceEl := range slice {
+			if el == sliceEl {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Fatalf("set contained unexpected element %v", el)
+		}
+	}
+}
diff --git a/slice.go b/slice.go
new file mode 100644
index 0000000..181cf8f
--- /dev/null
+++ b/slice.go
@@ -0,0 +1,87 @@
+package collections
+
+/*****************
+This section contains the alias API, which allows for receiver-style calling
+convention.
+*****************/
+
+// Slice is an alias over a Go slice that enables a direct receiver-style API.
+// For Slice, T must satisfy comparable.
+type Slice[T comparable] []T
+
+// Check if a slice contains an element. Calls SliceContains.
+func (sl Slice[T]) Contains(needle T) bool {
+	return SliceContains(sl, needle)
+}
+
+// Run an operator on every element in the slice, and return a slice that
+// contains the result of every operation. Calls SliceMap.
+func (sl Slice[T]) Map(op UnaryOperator[T]) Slice[T] {
+	return SliceMap(sl, op)
+}
+
+// AnySlice is an alias over a Go slice that does not enforce T satisfying
+// comparable. Any method that relies on comparison of elements is not
+// available for AnySlice.
+type AnySlice[T any] []T
+
+// Run an operator on every element in the slice, and return a slice that
+// contains the result of every operation. Calls SliceMap.
+func (sl AnySlice[T]) Map(op UnaryOperator[T]) AnySlice[T] {
+	return SliceMap(sl, op)
+}
+
+/*****************
+This section contains the direct API, which is a more traditional Go style
+API.
+*****************/
+
+// Check if a slice contains an element.
+//
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+// Allocations: None.
+func SliceContains[T comparable](haystack []T, needle T) bool {
+	for i := 0; i < len(haystack); i++ {
+		if haystack[i] == needle {
+			return true
+		}
+	}
+	return false
+}
+
+// Run an operator on every element in the slice, and return a slice that
+// contains the result of every operation.
+//
+// Time Complexity: O(n * m) (where m = complexity of operator)
+// Space Complexity: O(n)
+// Allocations: 1 slice, n elements.
+func SliceMap[T any](sl []T, op UnaryOperator[T]) []T {
+	result := make([]T, len(sl))
+	for i := 0; i < len(sl); i++ {
+		result[i] = op(sl[i])
+	}
+	return result
+}
+
+// Run a predicate on every element in the slice, and return a slice
+// that contains every element for which the predicate was true.
+//
+// Time Complexity: O(n * m) (where m = complexity of predicate)
+// Space Complexity: O(n)
+// Allocations: 2 slice, first with n elements, second is the first slice
+// resized if necessary.
+func SliceFilter[T any](sl []T, pred UnaryPredicate[T]) []T {
+	result := make([]T, len(sl))
+	resultIdx := 0
+	for i := 0; i < len(sl); i++ {
+		if pred(sl[i]) {
+			result[resultIdx] = sl[i]
+			resultIdx++
+		}
+	}
+	if resultIdx < len(result)-1 {
+		result = result[:resultIdx]
+	}
+	return result
+}
diff --git a/slice_test.go b/slice_test.go
new file mode 100644
index 0000000..7a18bf5
--- /dev/null
+++ b/slice_test.go
@@ -0,0 +1,13 @@
+package collections_test
+
+import (
+	"testing"
+
+	"github.com/RageCage64/collections-go"
+	"github.com/RageCage64/go-assert"
+)
+
+func TestSliceContainsDirect(t *testing.T) {
+	x := []int{1, 2, 3}
+	assert.Assert(t, collections.SliceContains(x, 1), "it didn't")
+}