ConstMap::mapWithKey

Returns a ConstMap after an operation has been applied to each key and value in the current ConstMap.

Description

public function mapWithKey(
  (function(Tk,Tv):Tu) $fn,
): ConstMap<Tk,Tu>

Returns a ConstMap after an operation has been applied to each key and value in the current ConstMap.

Every key and value in the current ConstMap is affected by a call to mapWithKey(), unlike filterWithKey() where only values that meet a certain criteria are affected.

The keys will remain unchanged from this ConstMap to the returned ConstMap. The keys are only used to help in the mapping operation.

Parameters

  • (function(Tk,Tv):Tu) $fn - The callback containing the operation to apply to the current ConstMap keys and values.

Return Values