Homework 7: Creating world in 3 days/steps

How to submit

When solving and testing the homework locally, make sure the HW4 Ecosystem package is available and loaded. You can load it with using Ecosystem, or use the provided local test runner, which loads the course copy from Homework07/OurEcosystem as a local module.

Put all your solution code in hw.jl; the submitted file must not include using Ecosystem. Zip only hw.jl (without its parent folder) and upload the zip to BRUTE. Before executing hw.jl, BRUTE loads the same HW4 version of Ecosystem described in HW4.

Homework (2 points)

Create a macro @ecosystem that should be able to define a world given a list of statements @add # $species ${optional:sex}

world = @ecosystem begin
    @add 10 Sheep female    # adds 10 female sheep
    @add 2 Sheep male       # adds 2 male sheep
    @add 100 Grass          # adds 100 pieces of fully grown grass
    @add 3 Wolf             # adds 5 wolf with random sex
end

@add should not be treated as a macro, but rather just as a syntax, that can be easily matched.

As this is not a small task let's break it into 3 steps. (These intemediate steps will also be checked in BRUTE.)

1. Define method default_config(::Type{T}) for each T in Grass, Wolf,..., which returns a named tuple of default parameters for that particular agent (you can choose the default values however you like).

2. Define method _add_agents(max_id, count::Int, species::Type{<:Species}) and _add_agents(max_id, count::Int, species::Type{<:AnimalSpecies}, sex::Sex) that return an array of count agents of species species with id going from max_id+1 to max_id+count. Default parameters should be constructed with default_config. Make sure you can handle even animals with random sex (@add 3 Wolf).

3. Define the underlying function _ecosystem(ex), which parses the block expression and creates a piece of code that constructs the world.

You can test the macro (more precisely the _ecosystem function) with the following expression

ex = :(begin
    @add 10 Sheep female
    @add 2 Sheep male
    @add 100 Grass
    @add 3 Wolf
end)
genex = _ecosystem(ex)
world = eval(genex)