feat: add iterator support

go.mod

@@ -1,6 +1,6 @@
 module go.bug.st/f
 
-go 1.22.3
+go 1.25
 
 require github.com/stretchr/testify v1.9.0
 

iter.go

@@ -0,0 +1,41 @@
+package f
+
+import "iter"
+
+// FilterIter takes an iterator and a matcher and returns only those elements that satisfy the matcher.
+func FilterIter[T any](values iter.Seq[T], matcher Matcher[T]) iter.Seq[T] {
+	return func(yield func(x T) bool) {
+		for x := range values {
+			if matcher(x) {
+				if !yield(x) {
+					return
+				}
+			}
+		}
+	}
+}
+
+// Map applies the Mapper function to each element of the iterator.
+func MapIter[T, U any](values iter.Seq[T], mapper Mapper[T, U]) iter.Seq[U] {
+	return func(yield func(x U) bool) {
+		for x := range values {
+			if !yield(mapper(x)) {
+				return
+			}
+		}
+	}
+}
+
+// Reducer is a function that reduces an iterator's elements to a single value.
+func ReduceIter[T any](values iter.Seq[T], reducer Reducer[T], initialValue ...T) T {
+	var result T
+	if len(initialValue) > 1 {
+		panic("initialValue must be a single value")
+	} else if len(initialValue) == 1 {
+		result = initialValue[0]
+	}
+	for v := range values {
+		result = reducer(result, v)
+	}
+	return result
+}

slices.go

@@ -9,6 +9,7 @@
 package f
 
 import (
+	"iter"
 	"runtime"
 	"sync"
 	"sync/atomic"
@@ -124,3 +125,16 @@ func Count[T any](in []T, matcher Matcher[T]) int {
 	}
 	return count
 }
+
+// RefIter takes a slice of type []T and returns an iterator that yields
+// pointers to each element of the slice.
+func RefIter[T any](slice []T) iter.Seq[*T] {
+	return func(yield func(*T) bool) {
+		for i := range slice {
+			if !yield(&slice[i]) {
+				return
+			}
+		}
+	}
+}
+