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Description
Proposal Details
It's a common task to iterate over a slice and modify its elements. For the following structure:
type element struct {
field int
}
var (
elements = []element{
{field: 1},
{field: 2},
{field: 3},
}
doubledElements = []element{
{field: 2},
{field: 4},
{field: 6},
}
)we have to use one of:
func TestDoubleWithRangeAndIndex(t *testing.T) {
// change base elements without MutableValues
// using indexing
for i, e := range elements {
e.field *= 2
elements[i] = e
}
if !slices.Equal(elements, doubledElements) {
t.Fail()
}
}or
func TestDoubleWithRangeAndPointer(t *testing.T) {
// change base elements without MutableValues
// using pointer to element (useful in case of neested loops
// or operations on more than one field)
for i := range elements {
e := &elements[i]
e.field *= 2
}
if !slices.Equal(elements, doubledElements) {
t.Fail()
}
}The proposal is to add MutableValues iterator to slices package:
func MutableValues[Slice ~[]E, E any](s Slice) iter.Seq[*E] {
return func(yield func(*E) bool) {
for i := range s {
if !yield(&s[i]) {
return
}
}
}
}Mutating of all elements of the slice can looks like:
func TestDoubleWithMutableValuesIterator(t *testing.T) {
// values in elements will be changed
for e := range slices.MutableValues(elements) {
// we can directly change element via pointer
e.field *= 2
}
if !slices.Equal(elements, doubledElements) {
t.Fail()
}
}Metadata
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