proposal: iter: Add functions for traversing several sequences.

[stanislav-pyatykh]

Proposal Details

The proposal is to add functions for traversing several sequences without creating intermediate containers:

// Concat returns an iterator that yields elements of the given sequences in order.
func Concat[V any](seqs ...iter.Seq[V]) iter.Seq[V] {
  return func(yield func(V) bool) {
    for _, seq := range seqs {
      for v := range seq {
        if !yield(v) {
          return
        }
      }
    }
  }
}

// Concat2 returns an iterator that yields elements of the given sequences of pairs in order.
func Concat2[K, V any](seqs ...iter.Seq2[K, V]) iter.Seq2[K, V] {
  return func(yield func(K, V) bool) {
    for _, seq := range seqs {
      for k, v := range seq {
        if !yield(k, v) {
          return
        }
      }
    }
  }
}

Example usage:

func print(a, b []int) {
  for v := range iter.Concat(slices.Values(a), slices.Values(b)) {
    fmt.Println(v)
  }
}

[gabyhelp]

Related Issues

• proposal: iter: Enumerate, Keys and Values functions #68887 (closed)
• proposal: x/exp/xiter: Add transformers between iter.Seq and iter.Seq2 #69702 (closed)

Related Discussions

• Concatenate iterators

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