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by metadat 677 days ago
I want to understand the purpose of maps.All().

In the example:

  m := map[string]int{"a": 1, "b": 2, "c": 3}
  
  for k, v := range maps.All(m) {
   fmt.Printf("%v:%v ", k, v)
  }
  
  fmt.Println("")
  
  for k, v := range m {
   fmt.Printf("%v:%v ", k, v)
  }
These both output the same thing. What's the point of the addition?

Slices.All() seems similarly redundant and pointless.

Surely I must be misunderstanding something, I hope.
2 comments
sakjur 677 days ago
They’re useful because they let you pass a slice or map to something built to handle the new func(func (…) bool) style iterators.

If I create a IterateOver(fn func(func (K, V any) bool)) function, you cannot pass a slice since that doesn’t match fn’s type, but if you wrap it with slices.All it’ll work.

link
ianlancetaylor 677 days ago
You can use it with other functions that use iterators. For example, here is code that makes a copy of a map keeping only the even keys.

  maps.Collect(xiter.Filter2(func(k, v int) bool { return k%2 == 0 }, maps.All(m)))
link