proposal: maps: add functions to filter and transform map values

[pixel365]

Proposal Details

I propose to add the following general-purpose functions to the maps package:

// FilterFunc returns an iterator with filtered key-value pairs.
func FilterFunc[M ~map[K]V, K comparable, V any](m M, filter func(K, V) bool) iter.Seq2[K, V] {
	return func(yield func(K, V) bool) {
		for k, v := range m {
			if filter(k, v) {
				if !yield(k, v) {
					return
				}
			}
		}
	}
}

// TransformValuesFunc modifies values ​​with a user-defined function.
func TransformValuesFunc[M ~map[K]V, K comparable, V any](m M, transform func(K, V) V) {
	for k, v := range m {
		m[k] = transform(k, v)
	}
}

[gabyhelp]

Related Issues and Documentation

• proposal: maps: new package to provide generic map functions (discussion)
• proposal: maps: add Diff, Intersect, CopyFunc, Filter funcs #68480
• proposal: slices: Add functions `Map` and `Filter` #68065 (closed)

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[seankhliao]

This is just xiter.Filter(f, maps.All(m)) and xiter.Map(f, maps.All(m)) from #61898
No need for specialized functions

[seankhliao]

Duplicate of #61898