Multiple dispatch

This allows to use the same function name applied on different arguments (types). Also known as multimethods, multiple dispatch is a mechanism to determine (at run time) which one of the functions should be called based on the type one or more of its arguments.

A first example

Assume we have a small space game with a spaceship firing missiles at asteroids. The various elements would be represented by the following data types:

data Moving-Body

x :: Int

y :: Int

vx :: Int

vy :: Int

data Ship extends Moving-Body

angle

data Asteroid extends Moving-Body

radius

data Missile extends Moving-Body

Now, if we wanted to write description functions for these, we could use:

function describe (s :: Ship) -> "This is a cool spaceship!"

function describe (a :: Asteroid) -> "This is an asteroid!"

function describe (m :: Missile) -> "...yet another missile"

objects-in-space :: [] of Moving-Body

objects-in-space = [Ship(...), Asteroid(...), Missile(...)]

do

print describe(objects-in-space.1)

print describe(objects-in-space.2)

print describe(objects-in-space.3)

The previous example would print all three different descriptions.

The same can be applied to several arguments and is the subject of the next section.

Handling collisions!

In the following example, we will handle the collison cases.

Ambiguities

Specifyic dispatch

Note: this will be implemented at a later stage