My gut pick is this one:
subset? =
fn (map1, map2) ->
in_other =
fn {key, value} ->
{:ok, value} == Map.fetch(map2, key)
end
map1
|> Map.to_list()
|> Enum.all?(in_other)
end
as it simply verifies that all the necessary key/value pairs are present and will stop as soon as that is not the case.
In this case I also prefer to use fetch/2 in order the leverage the underlying map functionality rather than relying on in/2’s macro magic even if it makes the code a bit more verbose (so be it).
One thing to be aware of is that the empty set is a subset of any other set - the same is true for empty maps.
