Map.update-exclamation-mark
You're seeing just the function
update-exclamation-mark
, go back to Map module for more information.
Specs
Updates key
with the given function.
If key
is present in map
then the existing value is passed to fun
and its result is
used as the updated value of key
. If key
is
not present in map
, a KeyError
exception is raised.
Examples
iex> Map.update!(%{a: 1}, :a, &(&1 * 2))
%{a: 2}
iex> Map.update!(%{a: 1}, :b, &(&1 * 2))
** (KeyError) key :b not found in: %{a: 1}