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This is available as Dict\map_keys in the www repository.

Returns a new dict where each key is the result of calling the given function on the original key

namespace HH\Lib\Dict;

function map_keys<Tk1, Tk2 as arraykey, Tv>(
  KeyedTraversable<Tk1, Tv> $traversable,
  (function(Tk1): Tk2) $key_func,
): dict<Tk2, Tv>;

In the case of duplicate keys, later values will overwrite the previous ones.

Time complexity: O(n * f), where f is the complexity of $key_func Space complexity: O(n)



  • dict<Tk2, Tv>