Add op.Add accumulator

iter/iter_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/BooleanCat/go-functional/v2/internal/assert"
 	"github.com/BooleanCat/go-functional/v2/iter"
+	"github.com/BooleanCat/go-functional/v2/iter/op"
 )
 
 func ExampleCollect() {
@@ -155,10 +156,7 @@ func TestForEach2Empty(t *testing.T) {
 }
 
 func ExampleReduce() {
-	fmt.Println(iter.Reduce(iter.Lift([]int{1, 2, 3}), func(a, b int) int {
-		return a + b
-	}, 0))
-
+	fmt.Println(iter.Reduce(iter.Lift([]int{1, 2, 3}), op.Add, 0))
 	// Output: 6
 }
 

iter/op/op.go

@@ -0,0 +1,6 @@
+package op
+
+// Add returns the sum of `a` and `b`.
+func Add[V ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | ~int | ~int8 | ~int16 | ~int32 | ~int64 | ~string | ~float32 | ~float64](a, b V) V {
+	return a + b
+}

iter/op/op_test.go

@@ -0,0 +1,18 @@
+package op_test
+
+import (
+	"fmt"
+
+	"github.com/BooleanCat/go-functional/v2/iter"
+	"github.com/BooleanCat/go-functional/v2/iter/op"
+)
+
+func ExampleAdd() {
+	fmt.Println(iter.Reduce(iter.Lift([]int{1, 2, 3}), op.Add, 0))
+	// Output: 6
+}
+
+func ExampleAdd_string() {
+	fmt.Println(iter.Reduce(iter.Lift([]string{"a", "b", "c"}), op.Add, ""))
+	// Output: abc
+}