Add TryCollect and Collect2 consumers and remove CollectErr

Author: BooleanCat

it/enumerate_test.go

@@ -3,7 +3,9 @@ package it_test
 import (
 	"fmt"
 	"slices"
+	"testing"
 
+	"github.com/BooleanCat/go-functional/v2/internal/assert"
 	"github.com/BooleanCat/go-functional/v2/it"
 )
 
@@ -17,3 +19,23 @@ func ExampleEnumerate() {
 	// 1 2
 	// 2 3
 }
+
+func TestEnumerateYieldFalse(t *testing.T) {
+	t.Parallel()
+
+	iterator := it.Enumerate(slices.Values([]int{1, 2, 3, 4, 5}))
+
+	var (
+		index  int
+		number int
+	)
+
+	iterator(func(i int, n int) bool {
+		index = i
+		number = n
+		return false
+	})
+
+	assert.Equal(t, index, 0)
+	assert.Equal(t, number, 1)
+}

it/exhausted_test.go

@@ -4,9 +4,7 @@ import (
 	"fmt"
 	"maps"
 	"slices"
-	"testing"
 
-	"github.com/BooleanCat/go-functional/v2/internal/assert"
 	"github.com/BooleanCat/go-functional/v2/it"
 )
 
@@ -19,23 +17,3 @@ func ExampleExhausted2() {
 	fmt.Println(len(maps.Collect(it.Exhausted2[int, string]())))
 	// Output: 0
 }
-
-func TestEnumerateYieldFalse(t *testing.T) {
-	t.Parallel()
-
-	iterator := it.Enumerate(slices.Values([]int{1, 2, 3, 4, 5}))
-
-	var (
-		index  int
-		number int
-	)
-
-	iterator(func(i int, n int) bool {
-		index = i
-		number = n
-		return false
-	})
-
-	assert.Equal(t, index, 0)
-	assert.Equal(t, number, 1)
-}

it/iter.go

@@ -2,7 +2,6 @@ package it
 
 import (
 	"cmp"
-	"errors"
 	"iter"
 )
 
@@ -127,20 +126,35 @@ func Find2[V, W any](iterator func(func(V, W) bool), pred func(V, W) bool) (V, W
 	return zeroV, zeroW, false
 }
 
-// CollectErr consumes an [iter.Seq2] where the right side yields errors and
-// returns a slice of values and all errors joined together.
-func CollectErr[V any](delegate func(func(V, error) bool)) ([]V, error) {
+// TryCollect consumes an [iter.Seq2] where the right side yields errors and
+// returns a slice of values and the first error encountered. Iteration stops
+// at the first error.
+func TryCollect[V any](iterator func(func(V, error) bool)) ([]V, error) {
+	var values []V
+
+	for v, err := range iterator {
+		if err != nil {
+			return values, err
+		}
+		values = append(values, v)
+	}
+
+	return values, nil
+}
+
+// Collect2 consumes an [iter.Seq2] and returns two slices of values.
+func Collect2[V, W any](iterator func(func(V, W) bool)) ([]V, []W) {
 	var (
-		values []V
-		errs   []error
+		lefts  []V
+		rights []W
 	)
 
-	for v, err := range delegate {
-		values = append(values, v)
-		errs = append(errs, err)
+	for v, w := range iterator {
+		lefts = append(lefts, v)
+		rights = append(rights, w)
 	}
 
-	return values, errors.Join(errs...)
+	return lefts, rights
 }
 
 // Len consumes an [iter.Seq] and returns the number of values yielded.

it/iter_test.go

@@ -30,7 +30,7 @@ func TestForEachEmpty(t *testing.T) {
 }
 
 func ExampleForEach2() {
-	it.ForEach2(it.Enumerate(slices.Values([]int{1, 2, 3})), func(index int, number int) {
+	it.ForEach2(slices.All([]int{1, 2, 3}), func(index int, number int) {
 		fmt.Println(index, number)
 	})
 	// Output:
@@ -59,7 +59,7 @@ func TestReduceEmpty(t *testing.T) {
 }
 
 func ExampleReduce2() {
-	fmt.Println(it.Reduce2(it.Enumerate(slices.Values([]int{1, 2, 3})), func(i, a, b int) int {
+	fmt.Println(it.Reduce2(slices.All([]int{1, 2, 3}), func(i, a, b int) int {
 		return i + 1
 	}, 0))
 
@@ -115,7 +115,7 @@ func ExampleFind_notFound() {
 }
 
 func ExampleFind2() {
-	index, value, ok := it.Find2(it.Enumerate(slices.Values([]int{1, 2, 3})), func(i, v int) bool {
+	index, value, ok := it.Find2(slices.All([]int{1, 2, 3}), func(i, v int) bool {
 		return i == 2
 	})
 	fmt.Println(index, value, ok)
@@ -124,24 +124,46 @@ func ExampleFind2() {
 }
 
 func ExampleFind2_notFound() {
-	index, value, ok := it.Find2(it.Enumerate(slices.Values([]int{1, 2, 3})), func(i, v int) bool {
+	index, value, ok := it.Find2(slices.All([]int{1, 2, 3}), func(i, v int) bool {
 		return i == 4
 	})
 
 	fmt.Println(index, value, ok)
 	// Output: 0 0 false
 }
 
-func ExampleCollectErr() {
-	data := strings.NewReader("one\ntwo\nthree\n")
-	lines, err := it.CollectErr(it.LinesString(data))
+func ExampleCollect2() {
+	indicies, values := it.Collect2(slices.All([]int{1, 2, 3}))
+	fmt.Println(values)
+	fmt.Println(indicies)
+
+	// Output:
+	// [1 2 3]
+	// [0 1 2]
+}
+
+func ExampleTryCollect() {
+	text := strings.NewReader("one\ntwo\nthree\n")
+
+	lines, err := it.TryCollect(it.LinesString(text))
 	fmt.Println(err)
 	fmt.Println(lines)
+
 	// Output:
 	// <nil>
 	// [one two three]
 }
 
+func TestTryCollectError(t *testing.T) {
+	t.Parallel()
+
+	text := new(failSecondTime)
+	lines, err := it.TryCollect(it.LinesString(text))
+
+	assert.Equal(t, err.Error(), "read error")
+	assert.SliceEqual(t, lines, []string{"o"})
+}
+
 func ExampleLen() {
 	fmt.Println(it.Len(slices.Values([]int{1, 2, 3})))
 
@@ -155,7 +177,7 @@ func TestLenEmpty(t *testing.T) {
 }
 
 func ExampleLen2() {
-	fmt.Println(it.Len2(it.Enumerate(slices.Values([]int{1, 2, 3}))))
+	fmt.Println(it.Len2(slices.All([]int{1, 2, 3})))
 
 	// Output: 3
 }

it/itx/iter.go

@@ -74,10 +74,16 @@ func (iterator Iterator2[V, W]) Find(predicate func(V, W) bool) (V, W, bool) {
 	return it.Find2(iterator, predicate)
 }
 
-// CollectErr consumes an [Iterator2] where the right side yields errors and
-// returns a slice of values and all errors yielded joined together.
-func CollectErr[V any](iterator Iterator2[V, error]) ([]V, error) {
-	return it.CollectErr(iter.Seq2[V, error](iterator))
+// TryCollect consumes an [iter.Seq2] where the right side yields errors and
+// returns a slice of values and the first error encountered. Iteration stops
+// at the first error.
+func TryCollect[V any](iterator func(func(V, error) bool)) ([]V, error) {
+	return it.TryCollect(iterator)
+}
+
+// Collect2 consumes an [iter.Seq2] and returns two slices of values.
+func (iterator Iterator2[V, W]) Collect() ([]V, []W) {
+	return it.Collect2(iterator)
 }
 
 // Len is a convenience method for chaining [it.Len] on [Iterator]s.

it/itx/iter_test.go

@@ -79,16 +79,27 @@ func ExampleFromMap() {
 	// Output: [2]
 }
 
-func ExampleCollectErr() {
-	data := strings.NewReader("one\ntwo\nthree\n")
-	lines, err := itx.CollectErr(itx.LinesString(data))
+func ExampleTryCollect() {
+	text := strings.NewReader("one\ntwo\nthree\n")
+	lines, err := itx.TryCollect(itx.LinesString(text))
 	fmt.Println(err)
 	fmt.Println(lines)
+
 	// Output:
 	// <nil>
 	// [one two three]
 }
 
+func ExampleIterator2_Collect() {
+	indicies, values := itx.FromSlice([]int{1, 2, 3}).Enumerate().Collect()
+	fmt.Println(values)
+	fmt.Println(indicies)
+
+	// Output:
+	// [1 2 3]
+	// [0 1 2]
+}
+
 func ExampleIterator_Len() {
 	fmt.Println(itx.FromSlice([]int{1, 2, 3}).Len())
 	// Output: 3