Map "putUntilAbsent" or similar?

[DartBot]

This issue was originally filed by [email protected]

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I'd like to run a function which generates a new key until I have a key that doesn't already exist in my Map. Once I've got a new key, add it and the value to the map. Is there a better way of doing this?

I cooked up putUntilAbsent(k, v, f()) in the class that implements Map.

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putUntilAbsent(k, v, fn()) {
  while (containsKey(k)) {
    k = fn();
  }
  this.Cache[k] = v;
  return v;
}

[kasperl]

Added Area-Library, Triaged labels.

[DartBot]

This comment was originally written by [email protected]

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Maybe "putWhenAbsent" is a better name..

[lrhn]

I think this is a little too specialized to be in the general map interface.

You can simulate this by:
  putWhenAbsent(Map map, var key, var value, keygen()) {
    bool put = false;
    puthook() { put = true; return value; }
    while (true) {
      map.putIfAbsent(key, puthook);
      if (put) return;
      key = keygen();
    }
  }

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Added WontFix label.