proposal: iter: add Empty function #66187
Comments
|
I know the code is contrived as an example, but couldn't you rewrite it as if cond {
if all := findAll(); all != nil {
for _, v := range all {
doItem(v)
}
}
}instead? And what is |
|
I prefer unnested code. func do(cond bool) error {
var all = iter.Empty[int]()
if cond {
var err error
all, err = findAll()
if err != nil {
return fmt.Errorf("failed to find all: %w", err)
}
}
for _, v := range all {
doItem(v)
}
return nil
}v.s. func do(cond bool) error {
if cond {
if all, err := findAll(); err != nil {
return fmt.Errorf("failed to find all: %w", err)
} else if all != nil {
for _, v := range all {
doItem(v)
}
}
}
return nil
}
I think it's less readable. var all = func(func(int) bool) {} // what's this!?v.s. var all = iter.Empty[int]() // I see, this is empty iterator. |
|
How about func do(cond bool) error {
if !cond {
return nil
}
all, err := findAll()
if err != nil {
return fmt.Errorf("failed to find all: %w", err)
}
if all == nil {
return nil
}
for _, v := range all {
doItem(v)
}
return nil
}instead? And again, what is I just can't see this kind of thing coming up very often. Maybe I'm wrong, but I feel like this should be added once it's proven to be an annoyance, rather than in advance as a counter to what seems likely to me to be a non-existent problem. |
|
Please consider the sutuation you can't early return by if !cond {
return nil
}because we need to do some after iteration for _, v := range all {
doItem(v)
}
doAfterIteration()
return nilI just want to say there are many codes which depends on iteration safety of nil slice/map. |
|
How about this case? func getIds() []int {
if condA {
return nil
}
somethingAfterA()
if condB {
return nil
}
somethingAfterB()
if condC {
return nil
}
somethingAfterC()
return getIdsImpl()
}
func do() {
for _, v := range getIds() {
println(v)
}
}When func getIds() iter.Seq[int] {
if condA {
return iter.Empty[int]()
}
somethingAfterA()
if condB {
return iter.Empty[int]()
}
somethingAfterB()
if condC {
return iter.Empty[int]()
}
somethingAfterC()
return getIdsImpl()
}
func do() {
for _, v := range getIds() {
println(v)
}
} |
Proposal Details
Add
Emptyfunction toiterpackage.This function returns empty iterator.
Implementation
Usage
This function is useful to replace slice/map implementation to iter implementation.
Please see following code.
This function do something to all item when
condis true.#65629 was declined, so range over nil function panics.
I have to rewrite like following.
When
Emptyfunction exists, I can migrate code easily.The text was updated successfully, but these errors were encountered: