proposal: src/iter: iter.Seq2.Keys() and iter.Seq2.Values()

[petern48]

Proposal Details

Basically the same as the maps.Keys() and maps.Values() functions, written here except for iter.Seq2 datatype. I found that the existing implementations for maps.Keys() worked exactly for what I needed. The function doesn't work for the iter.Seq2 type, so I ended up writing the below function myself, simply replacing the datatypes. Seems like a useful addition to the standard library. Happy to submit a PR myself if this is approved.

func Keys[K, V any](seq iter.Seq2[K, V]) iter.Seq[K] {
 	return func(yield func(K) bool) {
 		for k, _ := range seq {
 			if !yield(k) {
 				return
 			}
 		}
 	}
 }

// Same with func Values() ...

[gabyhelp]

Related Issues

• proposal: iter: Enumerate, Keys and Values functions #68887 (closed)
• iter: documentation improvements #70986 (closed)
• proposal: x/exp/xiter: Add transformers between iter.Seq and iter.Seq2 #69702 (closed)
• proposal: Go 2: range-over-function + range over types implementing iterator interface #65742 (closed)
• proposal: slices: funcs `CollectKeys` and `CollectValues` to collect from an iter.Seq2 #69706
• proposal: iter: convert between Seq and Seq2 #67334

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

see #61898 (comment)