playing in iex
Start IEx session by running iex -S mix at the root
of the project directory.
Aliasing a modules can be done with:
iex> alias IslandsEngine.Coordinate
iex> Coordinate.new(1,1)
iex> %Coordinate{row: 5}
** Argument Error something something
iex> alias IslandsEngine.{Coordinate, Guesses}
iex> guesses = Guesses.new
iex> {:ok, coordinate1} = Coordinate.new(1,1)
iex> {:ok, coordinate2} = Coordinate.new(2,2)
Adding coordinate1 to the set of hits with the Kernel.update_in/2 function.
update_in/2 takes a path to the nested data structure we want to update
and a function to transform its value.
update_in/2 will pass that structure into the function as the first argument.
iex> guesses = update_in(guesses.hits, &MapSet.put(&1, coordinate1))
What just happend is a transformation.
The original value for guess is unchanged yet.
We need to rebind it to the guess variable.
Once that rebinding happens, the original value will fall out of scope
and be garbage collected.
iex> guesses = update_in(guesses.hits, &MapSet.put(&1, coordinate2))
If we try adding coordinate1 again, it will not change much.
Islands
Within the body of new/2 there are two conditions we have to meet in order to produce
a valid island. The offsets/1 function has to return a list of offsets instead of an invalid island key error,
and add_coordinates/2 neeeds to return a MapSet instead of an invalid coordinate error.
If both of those conditions pass, we can return a tagged tuple with :ok
and the complete island.
In Elixir, the preffered way to handle multiple conditions like this is with the with/1
special form. This keeps all the validations in one place, and it gives us a single place
to handle any error that might come up.
Error
The else clause mathes any error that might arise and passes it on. We are expecting this to be one of two error types:
- {:error, :invalid_island_type}
- {:error, :invalid_coordinate}