exercism/elixir/dancing-dots/HINTS.md

Hints

General

• Read about behaviours in the official Getting Started guide.
• Read about behaviours on elixirschool.com.
• Read about behaviours in the documentation.
• Read about use in the official Getting Started guide.
• Read about use in the documentation.

1. Define the animation behaviour

• Use the @callback module attribute to define the desired functions.
• Each callback must specify the function name, list of arguments (their types) and the return value (its type).
• Use the given custom types dot, opts, error, and frame_number in the callbacks' definitions.
• Refresh your knowledge of typespecs to help with defining callbacks.

2. Provide a default implementation of the init/1 callback

• Define a __using__/1 macro in the DancingDots.Animation module.
• The macros' argument can be ignored.
• The macro must return a quoted expression.
• In the quoted expression, use @behaviour so that calling use DancingDots.Animation sets DancingDots.Animation as the using module's behaviour.
• In the quoted expression, implement the init/1 function.
• The default implementation of the init/1 function should wrap the given opts argument in :ok tuple.
• There is a macro that can mark a function as overridable.

3. Implement the Flicker animation

• Make use of DancingDots.Animation __using__/1 macro by calling this one special macro in the DancingDots.Flicker module.
• You do not need to implement the init/1 function. Its default implementation is enough.
• You need to implement the handle_frame/3 function.
• To detect "every 4th frame", you can check if the remainder when dividing it by 4 is equal to 0.

4. Implement the Zoom animation

• Make use of DancingDots.Animation __using__/1 macro by calling this one special macro in the DancingDots.Zoom module.
• You need to implement both the init/1 function and the handle_frame/3 function.
• Use the Keyword module to work with the options keyword list.
• There is a built-in guard for checking if a value is a number.