iterfunc experiment

go.mod

@@ -1,6 +1,6 @@
 module git.crumpington.com/public/jldb
 
-go 1.21.1
+go 1.22
 
 require (
 	github.com/google/btree v1.1.2

mdb/db-testcases_test.go

@@ -743,29 +743,25 @@ var testDBTestCases = []DBTestCase{{
 
 			first := true
 			pivot := User{Name: "User1"}
-			db.Users.ByName.AscendAfter(tx, &pivot, func(u *User) bool {
+			for u := range db.Users.ByName.AscendAfter(tx, &pivot) {
 				u.Name += "Mod"
 				if err = db.Users.Update(tx, u); err != nil {
-					return false
+					return err
 				}
 				if first {
 					first = false
-					return true
+					continue
 				}
 
 				prev := db.Users.ByID.Get(tx, &User{ID: u.ID - 1})
 				if prev == nil {
-					err = errors.New("Previous user not found")
-					return false
+					return errors.New("Previous user not found")
 				}
 
 				if !strings.HasSuffix(prev.Name, "Mod") {
-					err = errors.New("Incorrect user name: " + prev.Name)
-					return false
+					return errors.New("Incorrect user name: " + prev.Name)
 				}
-
-				return true
-			})
+			}
 			return nil
 		},
 
@@ -801,29 +797,26 @@ var testDBTestCases = []DBTestCase{{
 			}
 
 			first := true
-			db.Users.ByName.DescendAfter(tx, &User{Name: "User5Mod"}, func(u *User) bool {
+			for u := range db.Users.ByName.DescendAfter(tx, &User{Name: "User5Mod"}) {
 				u.Name = strings.TrimSuffix(u.Name, "Mod")
 				if err = db.Users.Update(tx, u); err != nil {
-					return false
+					return err
 				}
 				if first {
 					first = false
-					return true
+					continue
 				}
 
 				prev := db.Users.ByID.Get(tx, &User{ID: u.ID + 1})
 				if prev == nil {
-					err = errors.New("Previous user not found")
-					return false
+					return errors.New("Previous user not found")
 				}
 
 				if strings.HasSuffix(prev.Name, "Mod") {
-					err = errors.New("Incorrect user name: " + prev.Name)
-					return false
+					return errors.New("Incorrect user name: " + prev.Name)
 				}
+			}
 
-				return true
-			})
 			return nil
 		},
 

mdb/equality_test.go

@@ -1,7 +1,6 @@
 package mdb
 
 import (
-	"fmt"
 	"reflect"
 	"testing"
 )
@@ -20,18 +19,16 @@ func (i Index[T]) AssertEqual(t *testing.T, tx1, tx2 *Snapshot) {
 	}
 
 	errStr := ""
-	i.Ascend(tx1, func(item1 *T) bool {
+	iter := i.Ascend(tx1)
+	for item1 := range iter {
 		item2 := i.Get(tx2, item1)
 		if item2 == nil {
-			errStr = fmt.Sprintf("Indices don't match. %v not found.", item1)
-			return false
+			t.Fatalf("Indices don't match. %v not found.", item1)
 		}
 		if !reflect.DeepEqual(item1, item2) {
-			errStr = fmt.Sprintf("%v != %v", item1, item2)
-			return false
+			t.Fatalf("%v != %v", item1, item2)
 		}
-		return true
-	})
+	}
 
 	if errStr != "" {
 		t.Fatal(errStr)

mdb/index.go

@@ -1,6 +1,7 @@
 package mdb
 
 import (
+	"iter"
 	"unsafe"
 
 	"github.com/google/btree"
@@ -111,32 +112,40 @@ func (i *Index[T]) Max(tx *Snapshot) *T {
 	return nil
 }
 
-func (i *Index[T]) Ascend(tx *Snapshot, each func(*T) bool) {
+func (i *Index[T]) Ascend(tx *Snapshot) iter.Seq[*T] {
 	tx = i.ensureSnapshot(tx)
-	i.btreeForIter(tx).Ascend(func(t *T) bool {
-		return each(i.copy(t))
-	})
+	return func(yield func(*T) bool) {
+		i.btreeForIter(tx).Ascend(func(t *T) bool {
+			return yield(i.copy(t))
+		})
+	}
 }
 
-func (i *Index[T]) AscendAfter(tx *Snapshot, after *T, each func(*T) bool) {
+func (i *Index[T]) AscendAfter(tx *Snapshot, after *T) iter.Seq[*T] {
 	tx = i.ensureSnapshot(tx)
-	i.btreeForIter(tx).AscendGreaterOrEqual(after, func(t *T) bool {
-		return each(i.copy(t))
-	})
+	return func(yield func(*T) bool) {
+		i.btreeForIter(tx).AscendGreaterOrEqual(after, func(t *T) bool {
+			return yield(i.copy(t))
+		})
+	}
 }
 
-func (i *Index[T]) Descend(tx *Snapshot, each func(*T) bool) {
+func (i *Index[T]) Descend(tx *Snapshot) iter.Seq[*T] {
 	tx = i.ensureSnapshot(tx)
-	i.btreeForIter(tx).Descend(func(t *T) bool {
-		return each(i.copy(t))
-	})
+	return func(yield func(*T) bool) {
+		i.btreeForIter(tx).Descend(func(t *T) bool {
+			return yield(i.copy(t))
+		})
+	}
 }
 
-func (i *Index[T]) DescendAfter(tx *Snapshot, after *T, each func(*T) bool) {
+func (i *Index[T]) DescendAfter(tx *Snapshot, after *T) iter.Seq[*T] {
 	tx = i.ensureSnapshot(tx)
-	i.btreeForIter(tx).DescendLessOrEqual(after, func(t *T) bool {
-		return each(i.copy(t))
-	})
+	return func(yield func(*T) bool) {
+		i.btreeForIter(tx).DescendLessOrEqual(after, func(t *T) bool {
+			return yield(i.copy(t))
+		})
+	}
 }
 
 func (i *Index[T]) Count(tx *Snapshot) int {

mdb/index_test.go

@@ -1,9 +1,8 @@
 package mdb
 
 func (i Index[T]) Dump(tx *Snapshot) (l []T) {
-	i.Ascend(tx, func(t *T) bool {
+	for t := range i.Ascend(tx) {
 		l = append(l, *t)
-		return true
-	})
+	}
 	return l
 }