Homework 7: Creating world in 3 days/steps

How to submit

Put all the code of inside hw.jl. Zip only this file (not its parent folder) and upload it to BRUTE. You should assume that only

using Ecosystem

will be put before your file is executed, but do not include them in your solution. The version of Ecosystem pkg should be the same as 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 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.)

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).
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).
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)